Let me start off, I'm neither MD nor OD (I start med school in the fall) but my father was an OD and he used to use me as his test subject for new allergy drops, so from the patient standpoint I know a good bit about them.
You're right, restasis isn't designed for allergies, but it works wonders on mine. For the first 3 months I was on it, I used twice a day (wake up and bedtime) then tapered to just bedtime. No allergy problems, in the eyes at least, since then. Before this I'd tried Patanol and Elistat (big fan of both), Alocril (worst ever), Alrex (which I've found is really good at keeping the allergies down after stabilizing with something else), and Lotemax if it gets really, really bad (but never as a long term fix, of course). However after about 3 months, give or take a week, Restasis was better at controlling my allergies than any of these others. I even tried going off Restasis for about a week and back to Elistat, didn't work as well.
Anyway, to make a real long, drawn out story short, here is what dad did in terms of restasis and allergic conjunctivitis: for people who only occasionally needed eye drops, he'd give Patanol or Elistat; for patients who had a severe enough case to require daily drops of either of those, he would try restasis first. Most of these patients reported that their allergies got significantly better, so yes; I'd say Restasis works well with allergies.