Interesting. As a sailor who has navigated a ton of draws, lifts, swings, and bascules, I can tell you that they almost all of them run on a different schedule, and the instructions to marine traffic are usually printed on a NOAA chart.
In high boat traffic areas, the bridges are usually left open until needed. But in areas with both high boat and bridge traffic, they often either run on a schedule or on-demand. The standard call from a boat can be either via radio on Channel 16 (unless otherwise posted) or by one long blast of the horn.
In Mystic, CT the NEC swing bridge over the Mystic River runs on a schedule, as does the Route 1 Bascule. They try to synch them so that when traffic clears one, they'll be ready at the second.
With the exception of swing bridges, most of these bridges operate on extraordinarily low horsepower, and they are very carefully balanced. Sounds more like someone at HQ dropping a operational command onto a local district without knowing the particulars.
Jon 
