I have to go through that bridge all the time and I have fished from it. When I fish from it I keep my lines out of the lanes that the boats go through and I expect the people fishing on it when I go through, with my boat, to do the same. That being said...you gave them plenty of opportunity to get their lines out of the way for the whole 30 seconds or so it would take for you to pass under the bridge...so tough luck to them if you run over their lines and they lose their bait. You were more than polite!
You did the right thing and gave them the time to reel in. You did much more than when I was fishing at Governors Island bridge one time and a big cruiser went under the bridge at full speed. He docked his boat a short ways off. Everyone had some choice words for him, and he never even looked our way!!!
You did right. I had to dock at the town docks in Alton bay on saturday, all the docks were busy with fisherman/woman, no place to pull in, I idled for a few moments(couple minutes most) until one yelled out at me, "do you need to dock?" I said yes, he pulled his stuff in and I gave him a big thank you. He continued to fish there, when I was leaving he pulled in his stuff and let me on my way. I would have done the same if I was in his shoes. Common Courtesy rules. I think he lost less than 5 minutes of fishing by being courtieous.
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.