Lots of words there but not much detail.  If T-Mobile have their own Lightening nodes then adding a network integrated Lightening wallet would be a good way to introduce people to Bitcoin.  Especially if they could create a good, easy to use UI.

The OP mentions Polygon which I don't know anything about but I don't think it has anything to do with Bitcoin.

As far as this mining joint venture goes, it could be good for T-Mobile if they want to add Bitcoin to their balance sheet but do it by mining rather than purchasing.  Perhaps they already have some technical infrastructure that could be adapted to mining Bitcoin.  I don't see how that involves their phone networks or customers though.  Big firms going in on Bitcoin should be seen as a good thing as long as they aren't just dropping press releases with crypto buzzwords to get some media attention.