It's a mini Rubber-Tyre Metro for cargo. Low RoW maintenance (I think), high vehicle maintenance/wear, high energy usage.
The challenge to me: "just put it underground" isn't nearly as easy as people seem to think. There's a lot of people-placed stuff underground, and the companies doing it have likely been around longer than you, are pretty regulated, and nobody is going to want to change any of that for your Sandwich Delivering Subway. Especially because it is limited in purpose (cargo delivery, and fairly small cargo at that.)
Then there's all the shit that's in the ground not from humans. Roots. Boulders. Water. It's really fucking expensive to dig or tunnel, and there's no way delivering sandwiches and amazon packages is going to pay enough for it.
Assuming all that works out, there's still the matter of energy efficiency (which is terrible for RTM), speed, and capacity. I'm sure they can scale the "train" up to at least a few containers particularly if the container 'cars' are self-powered but non-rail vehicles use a lot of power. That means heat, not just the expense of the the power and hassle of either storing or transmitting it.
This does solve the main problem with pneumatic systems - even more tightly constrained cargo size limitations and massive power consumption.
Frankly, the Dutch are giggling at all this, I'm sure, because "just build a protected bike lane or shared-use path" is a much cheaper, easier, multi-benefit idea. Then not only can people get their sandwiches and packages delivered via a guy on a bike in a very energy-efficient way (a cargo bike uses about a tenth of the electricity even the best EV cars do), but they can safely bike to/from their office complex or home to other places. You've got something emergency vehicles can use in a pinch, too.