Maybe it's just me, but every time for the last 3 times I've tried warping to someone in a city instead of re-attempting a join to the city they're in whenever I got that error. Every time it's worked and I've successfully joined.
Fluke or does it work? Someone besides me needs to test this out.
I wouldn't think it would work, but it seems to. Iunno.
--- If you're reading this, you just lost the game. If you are upset about losing the game, I suggest you calm yourself by having a nice, cool, refreshing the game