Tow separate issues...

FAA: How much RW can you credit towards a FW ATP? See the FARs.

Airlines: Depends on each airline. Nowdays many may simply require an R-ATP of any sort. But some have always had their own minimums. SKW for example will accept a military R-ATP but will only accept a certain amount of helo time on a 2-for-one RW to FW basis. For a 750 hour mil R-ATP you would need 500 FW + (500 RW/2) = 750 which SKW will count. So you could have a mil R-ATP based mostly on RW time (500 RW + 250 FW) but still not be eligible to work at SKW.

You'll need to research each airline individually.