a) bugged the hell out of Nortel's ottawa area offices, both physically, by rootkit, and by getting their own people hired to physically smuggle out documents and design data
b) Copied the entire DWDM / optical transport product line
c) Released a nearly identical product a few years later, and sold it at a ridiculously low price, effectively killing Nortel.
Many years later the vacant ex-Nortel office buildings came up for lease. One of the candidate tenants for that large of an office space were parts of the Canadian federal government, ministry of defence, etc. Every serious tenant passed on the space because it's so riddled with bugs.
https://ottawacitizen.com/news/national/defence-watch/the-my...
https://www.ctvnews.ca/canada/dnd-may-abandon-1b-move-to-for...
https://www.theglobeandmail.com/news/politics/department-of-...