I (personally) think it ($50 plan) is just so crazy it might work.

Customers are frustrated about the complexity of the plans, bills, etc. This simplifies the billing and their workers to sell something to potential customers that much easier "Your bill will be $50, period".

I think they will see a huge boost in subscribers, and while they may lose some of their margins on data plans, most likely even people who don't really use the data aspect will get on the plan because a) they understand it b) its probably about the same (or less) than what they were already paying.

If they can keep up with network capacity, it could be a huge payoff in the longrun.