I do not know about Sprint Unlimited but I do know about T-mobile and now Verizon offers a T-Mobile like plan
So many GIGS are FULL SPEED AHEAD and then you drop to watching grass grow but you still get data.. Enough to be useful for mapping and such but not streaming video.
Of course.. it's been a long, long, long time since I burned up all my high speed (2013 in fact, April (My wife died on Mar-31 that year and I had a lot of documents that needed to be E-mailed back and forth between insurance companies and others in order to settle assorted affairs, I went over by 1` GIG. or less.)