Amongst those applications were undoubtedly a bunch of systems that are literally the mobile network itself...
Yes, yes, yes. Thing is, there was a clear lack of urgency here. The timelines you cite are for your case, and whatever requirements, budgets and deadlines you suffer. T-Mobile made a bad bet in 2008, and the writing has been on the wall for years now, and viable alternatives have been available at least as long. Were T-Mobile competently managed, they certainly had the means to meet the necessary deadlines. Instead, they made yet another bad bet trying to litigate against pirates.
The correct bet today is container orchestration and open-source based virtualization tools that aren't at the mercy of inveterate rent seekers. There are many ways to skin these cats, and the fact that T-Mobile has slouched into its current unfortunate position is entirely T-Mobile's fault.
Also, the argument that only "two calls" where made and, therefore, a team of 20 people is somehow ridiculous is specious. Support contracts at this scale involve far more than picking up a phone during business hours, and Broadcom will have absolutely no difficulty poking that argument full of holes.