I have not come across it; you possibly could achieve it by shutting off the replaygain (enabled by default) and processing those files containing ads with other software; but I'd first check that this hasn't already been done (and your ads are thus sounding "too quiet" because they are "fighting" the replaygain).

In any case the practice is now discouraged worldwide (it may even be illegal in some nations!) and is the sort of thing that actually gets regulators bothering with online broadcasting that they normally leave alone. More importantly it can annoy your listeners to the point the whole practice is counterproductive.

Better to have all your programme material at the same level (which replaygain tries to do but can end up still causing too many level variations). I don't run ads on my online station (which is more an experiment/hobby project; used to be a full time broadcast engineer but this isn't an enjoyable job any more) but process the shows manually to get them to a reasonable level (probably louder than they should be but not too harsh).

The misuse of Optimods for this purpose has got to a point where Orban now give away the loudness meter as freeware to improve their brand reputation (it is worth downloading)