Yes. It doesn't hurt to accept an offer and then politely withdraw prior to the start date. I know several that accepted and even started at JB/LCC/ULCC while waiting on an interview or start date at their preferred destination. If you want brand x, but they haven't give you a class date yet, go ahead and start at brand y. I know at least 2 guys that had DAL class dates months in the future, so they started at UAL just to get a paycheck. One left during sims and the other left after OE. You've burned that bridge, but you don't really care.