I read the portion of the filing that is being referenced in the article and it makes it seem as though both Sprint and T-Mobile are in a dire position. It's funny that despite all that has been stated, both carriers have 5G plans going out at least 6 years from now prepared already, should they be forced to operate separately.
The main issue presented is that Sprint can't deploy 2.5GHz 5G in rural areas because they don't have the money to do so. The only way to get more money is to have more customers. Because of Sprint's poor network perception, the only way for Sprint to get new customers is to lower prices. And because of low prices, Sprint can't make as much money off of their customers so they're stuck in a loop.
T-Mobile on the other hand has the money to build a broad 5G network over 600MHz, but they don't have the spectrum to provide 5G speeds like Sprint can. So they'll be able to claim the title of the largest 5G network by square mileage but with speeds that aren't much better than current LTE speeds. Sprint will a larger network capable of providing faster speeds. Basically, T-Mobile won't be able to compete effectively in the 5G space in terms of offering "true 5G experience" to their customers until they can get everyone off of LTE which isn't happening soon.
The solution is that in merging, the New T-Mobile will be able to deploy 2.5GHz over a large area so that more people can have access to those higher speeds that they wouldn't get by 600MHz only or because of Sprint's smaller network.
Yeah, Dish could have invested all that money that they invested in spectrum on Sprint's network instead. They could have brought the AWS-4 25x20 band of spectrum to sprint to strengthen Sprint's midband position, they would not have needed to bid on the AWS-3 auction and they could have probably acquired a 10x10 band of 600MHz.