If the masking tape you are trying to remove is only on the edges and as you say it is very well stuck and you can't get it to peel off then you could remove it by carefully rubbing it with some emery / sandpaper . Not sure about the 2 pieces of glass though . You don't want to remove all the tape if it is holding the 2 sheets of glass together .If the tape on the edge can't be seen then why not leave it .