I'm thinking Sprint is waiting until they get more coverage and then you'll see a dramatic update in the coverage map. At least I hope that's what it is.
For all of the doubters that Son isn't behind Sprint.
I think we are past the bottom of the V and Sprint is on its way back up.
http://www.businessinsider.com/ap-softbanks-annual-profit-drops-27-pct-on-sprint-woes-2016-5
There we go. I disabled my CA as per Tim's suggestion and was able to sit on the 3rd carrier for short time. If there is any other information you'd like, let me know and I'll do what I can to get it.
I am getting blips of what I believe to be a 3rd B41 carrier up North of Seattle in Lynnwood. I can't get a lot of information because it jumps off real quick but was able to get a quick screenshot in SCP.