I tend to go with Carelton here. Not as black and white as it appears on paper. For really strong sprinters who are experienced on the track, I think they will do better on a track bike. For roadies without much track experience, they are going to do better on a road bike (especially with a little coaching on selecting a starting gear where they only have to shift ONCE).

At the club event to which the OP refers, they allow road bikes in order to be inclusive. It's a lot of fun, and for many people, their first exposure to track. All the trackies use their track bikes. Last year, out of 70+ riders, the top 9 times were all track bikes (that in itself doesn't tell us anything, really... selection bias)... and the top road bike time was 4 seconds off the fastest time.