can't say. But from my personal experience working for NEV's and attending nearly every ETSI workshop on 5G, SDN and other Future-Network topics I dare to claim that the IP theft, at least
as reported by the media isn't true and most certainly smells politically motivated. Let me explain: from the late 90ies to the mid 2000 there were several rounds of mergers, consolidations in Telco, Siemens-COM, Nokia, A/LU, Ericsson all consolidated by shutting down major R&D departments by moving to China. In some cases across cheaper EU countries e.g. Italy, Croatia, etc sites just disappeared without moving but simply the consolidation of the portfolio led to a lot of people losing their jobs (again Italy especially had a lot of people working for NEV's). Some employees left the country, others managed to find a similar job with operators (but only in areas of acceptance testing, O&M, etc but not actual R&D). When Huawei swooped in to the rescue at these sites they could simply employ these guys who did the same job for the other players (after all it's all the same tech thanks to ETSI/3GPP standards so skills+experience are highly portable). And when you ask somebody to work on a system who has actually built an almost identical thing for the competitor (again identical because of standards) you have a head start.
What I want to say is that this wasn't some cloak+dagger operation as the US media paints it. When I say US media one must also consider the amplification of these news from other FVEY members - especially Australia who were very vocal about Huawei being a security risk - all very heavily involved in amplifying this manufactured outrage.
Another reason why the IP-theft angle (as reported in the West) is true but still exaggerated is that from what I have seen at the standardization meetings (again since mid-2000 till today - which is when LTE/-a were conceived is that Huawei was unlike their Western competitors very aggressive in innovating. I can't say the same thing about the delegates from Ericsson, A/LU, Siemens, Nokia which sent (quite old) people that were promoted away internally to look after these bureaucratic process. Huawei outperformed all of them (especially in 4G, 5G, SDN and the Future-Netwerks/IGN even M2M/IoT topics). They invested incredible amounts of time and money in innovation (through the standards path) almost like a start-up, which can't be said for the others and set up bodies in China (CENELEC) to ensure being on par with ETSI regs.
What hurt the established (big) guys most is that they actually thought like a start-up. If you worked at Huawei as a junior in Italy and other sites, you were allowed to move across departments and fields getting a well rounded picture of how the telco-sector works. If you wanted to gain the same experience with the big guys you'd have to stay 15-20 years in the company as opposed to 3-5 with Huawei. This is why Huawei engineers are highly sought after by other telco firms.
Lastly Huawei has been always competing on price. I got downvoted for saying this before here because people only saw the price-tags of the latest UEs like the P-range etc, but this isn't what we're talking about when we speak about NEV's (and from a security pov the risk isn't so much in the handsets but the rest of the infrastructure that makes the lions share of the R&D work). Huawei kit was (and still is) the worst and most shoddy equipment you can get in terms of Interoparability. (IOT means "interoperability testing" in this context and the industry used to employ whole departments in this field of work). Despite the crap quality they could sell their wares very cheaply across Africa and emerging countries (often to questionable regimes, ... but so did all the others only that their prices eventually ended up being to high once Huawei entered that regional market). So if it wouldn't be Huawei selling custom-made Lawful-Intercept (LI) to these dictators it would still be the established players doing it ...
The only thing that has changed in this game is the perception of how China is viewed in the world. Trust is a fickle thing and once you start playing with protectionism and trade-war that trust is over and from a security POV you have no other choice than re-think your supply-chain. Also to be fair to the established NEVs: Huawei sold their kit across the globe and still operates R&D centers across Europe employing thousands, the established players entered China and moved a large amount of innovation into China, the playing field wasn't equal. Huawei could tap into the know-how overseas and back home, while the established players operating in China faced a lot of restrictions.
Damn this is getting long, last point: if you are able to undercut your competitor at a loss (because you're propped up by your own government) there is simply no way for the others to compete with you. This is the kicker IMO and not the topic of Huawei being a natsec threat (which only is a symptom once trust broke down).
EDIT: TL;DR I'm not saying they didn't steal things but the information is twisted the way it is reported. And if we speak about backdoors we'd have to equally speak about threat-models and here backdoors are only tangentially interesting since the vulns that stem from shoddy engineering (hello crappy ASN1 parsers) are much cheaper to harness than some hypothetical purpose-made backdoor that costs millions to implement and keep covered-up. (Occam's razor)