Well, you see the B-wings in multiple shots when they're jumping from Sullust, then in a couple of shots when approaching the Death Star and opening S-foils, and in two more shots when they're pulling up. After that, no trace of them whatsoever.
They're also the only fighter which is never seen firing. Even the Y-wing and A-wing are both seen firing their lasers once (and the A-wings of course also firing missiles at Executor's dome).
I'm sure Adywan will insert a few into the background during the fight scenes, though.
P.S. Extra cookie for whoever knows in which scene the A-wing is seen firing its lasers, it's pretty easy to miss.