It all depends on what the specific airline hiring requirements are - and most airlines have no problem in telling anyone what the requirements are for their airline. I would say, call the airline for whom you want to work and ask them straight out.

The move to require an ATP to fly the line didn't have anything to do with the "level" of certificate held - but it was to be sort of a shorthand for saying the rules were now going to require the person in the right seat to have more "experience" (remember this was after the Colgan accident) and the 250 hour requirement for a Commercial Certificate seemed to be somewhat "thin" in the minds of many ... and they thought that a minimum of 1500 hours (ATP requirement) would surely be one way of sounding like a logical way to acquire that desired experience. So the real push was to find a way to say that inexperienced pilots weren't or shouldn't be flying in an airline cockpit. Unfortunately, while it may have been a well-intended effort, as most here know, any specific number of hours doesn't necessarily translate to experience OR competency. Having 1500 hours around a VFR traffic pattern is still 1500 hours. I hope I don't get into trouble saying this ... (yeah, I know) ... but, often the solutions that are seen after an accident is merely your friendly, neighborhood regulator trying to satisfy the isolated verbiage without making anyone mad. These kinds of decisions normally come from someone (or some ones) at the top of the regulatory food chain. The analogy that "cream" floats to the top is often used to describe the best usually getting ahead ... but, if you look at "cream," it's ultimately the source of artery clogging, heart problems, shortness of breath, and an overall shortening of a normal life span. To me, a person with that kind of propensity doesn't sound like someone that any realistic aviator would want laying down the law ... of course, that's my opinion only.