Another way is to take off the molding/strips, then take off the bumper cover by removing all the little push in plastic fasteners. The rebar will be left secured to the car.
Then you either need to find a way to get the bolts that hold the bumper shocks onto the body, or drill a hole in the rebar so you can fit a socket on it. You'll need to remove the rebar with the shocks attached if you can't get those big bolts out.
I think for the rear you might even be able to remove a few of the shock bolts from inside the trunk. It was the front that I think I had to drill, it's been a while since I've done it on an e30, but it can be done since I remember those bolts always being seized.