Anyone can now conceal carry in ME without a license. If you don't have a NH P&R you need to inform a cop you're carrying if you get pulled over.
I wasn't aware that an NH P&R counted as a "permit". I would figure that "permit" would be either a real maine license or a license from a state that ME actually has reciprocity with, and Maine isn't one of them. Otherwise nobody would have bothered to get a Maine license.
-Mike