I've never seen 4.0 #1 singles player on a 4.5 team. If you didn't get DQed or bumped after a few matches, USTA is not doing it's job (unless you played on the worst 4.5 team on the planet). You proved my point though
If I went through the details of my year I don't know that I would fully prove your point, but yes it is possible to play up. I pretty much had to beat everyone on the team to get my spot, but a lot of this was due to the captain.