They used them all the time. They even mounted the boys to a Universal carrier.
lol, how did you come across this!I don't know, but here's a training video made by Disney for training Canadian Army on using anti-tank rifles!
https://www.youtube.com/watch?v=AlJD0pZp4eQ
In '42 the US Marine raiders successfully used Boys AT rifles in the South Pacific.
You would think the antitank rifle would have been god for something besides tanks. But maybe nobody wanted to carry that thing. Could have used it to shoot through buildings to flsh the Nazis out. The piddly .303 couldn.t go through concrete walls.