I don't think so... I tried that a while back but I belive my particular ballast load tested the bulbs and would not operate. Some ballasts can "sense" what wattage of bulbs they are powereing. Thena gain, maybe I was wiring it wrong. This was a while ago and my first forray into DIY lighting.
A 4F32T8 ballast (one circuit per bulb) will most likely overdrive the bulb. Most electronic xF32T8 ballasts will automatically sense a 2' or 4' bulb but I don't think it will go down to a 15W bulb without overdriving it.
Here's an example of the ballasts you are looking for, keep in mind that some have slightly different codes (15 is the watts, T8 is the diameter), the important thing is that it is made to drive a 15W fluorescent or 13W CF (same ballast):