If it is clearcoat overspray (and you can't get the shop to fix it for you) you can use a pure polish. They remove paint from the body, so they'll work on the lens too. Just be careful not to get "overzealous" as the plastic may be fragile and break/crack from too much effort.
If you have a thick amount (drips) you might try a laquer thinner and Q-tip to get rid of the majority before polishing. Again, be careful not to get the thinner on the plastic, as it can "melt" the plastic too.
Really, though, even if it's not an insurance claim, if the shop did something to them, the shop should be willing to take care of it, including replacing the lenses if need be.