I concur after visiting that the transfer staff is very helpful and I had no problem with them printing my onward BA boarding pass at the transfer desk. Be careful with electronic boarding passes in Muscat since this seems to throw the front-line security and immigration people for a loop. Also, they seem to have issues scanning them even when they try at some checkpoints. I got by with an electronic boarding pass (after being persistent and making them continue retrying scanning it) on one of my journeys through Muscat but I HIGHLY recommend you not risk it and get a printed copy to make your journey through security and exit controls easier.