The consummation of Sprint and T-Mobile's merger, in addition a whole slew of other consequences, means two cellular networks are coming together. The New T-Mobile is already building on Sprint's mid-band 2.5GHz spectrum licenses — prized for giving a balance of speed and coverage for 5G — in a couple of major cities while Sprint customers already roaming on T-Mobile LTE can soon access 600MHz 5G if they have the right phone.
The company announced mid-band 5G is now available for T-Mobile customers in parts of Philadelphia with speeds of up to 600Mbps and will soon be available in pockets of New York City. It has also made progress on its low-band 5G — with the broadest land range possible and slight speed improvements above LTE — in Detroit, St. Louis, and Columbus, Ohio.
T-Mobile already started letting Sprint customers roam on its LTE network since before the merger closed as a goodwill gesture earlier on in the coronavirus outbreak. However, it will also let Galaxy S20 5G owners on Sprint to start using its 5G spectrum later this month — this should include the 600MHz grid as well as new 2.5GHz sites.
As far as what's been announced to this point, customers on the Magenta side won't be able to roam in Sprint's existing 5G cities or its LTE network for the time being as some reconfiguration needs to be done before everyone can access the combined network without hassle. Baby steps do come before giant leaps, after all.