Not an expert but because Taxi doesn't have a clear coat like T2 era games, I would use the chemical approach. Lift a piece of Mylar via a blade and grip it and maintain firm, even tension on it. Then squirt white spirits the Mylar and playfield meet and let it weaken/dissolve the glue. The Mylar will eventually release due to the tension. I found this method provided minimal to no paint lifting.

Do not use the freeze method at all. Heat is another option but the above I believe will give the best results.