I am not sure which bridges you mean. I was able to get under all bridges by lowering my antenna except the train bridge over the industrial canal under the I-10.

My boat is a Bertram 54, my air draft with antennas down is under 20 feet.

The train bridge near the seabrook bridge was open and I did not communicate with it. The other train bridge responded to a VHF hail from the tug on the other who hailed it to open. I arrived during daylight hours and there was commercial traffic going through albeit with a 45 minute wait.

I too could get no answers which is why I posted the question here. Hope that helps.