I think you have an implied right of way, if it were only a couple of guys I never stop at the bridge at Squam, they pull the lines out as soon as they see a boat coming and when they go by they put em right back in. I don't even ask, I just put my way through.
But if they are shoulder to shoulder I'm sure they are reluctant to move (might loose their place) but that thier problem with the other people on the bridge, not yours.