Any idea how old the tint is? I am the third owner of my 89. The second owner told me the windows were tinted when he bought the car in 92. That means I was trying to unglue something that was glued at least 15 years ago. I tried every trick mentioned above and nothing worked. It was bubbled in the back and it seems like the plastic bubbled but the glue just melted to the glass that much stronger.
I managed to damage several of the lines trying various tricks. Where the tint did not bubble the tint was stuck to the lines stronger then the lines were stuck to the window so pulling up that tint broke the lines. Where it did bubble the tint was easy to pull off but the window was coated with a layer of rock hard glue.
Finally I had half the lines broken, holes in the tint, and was much worse off then when I started. I figued I could not go back, so I took a razor to it. I got the tint off, but have no rear defroster now. Since it is mostly driven in the summer I was not terribly upset, but wish I had just left it alone.
If you decide to go for it I would recommend doing a side window first. I only wanted the back done and had planned to leave the side alone. I should have started on the sides to find the best way to do it, then done the back. I would have found out a razor was the only way the left the back alone.