Frozen Brake Line Fitting

I've been replacing the old brake hoses on our Cordoba and hit a snag. The fronts went fine but in the back I had some trouble. I was able to break the line loose from the hose but the tubing is seized inside the fitting. I've been soaking it in PB Blaster for the last couple days but still no luck. Of course I don't want to twist the line off so I was wondering if there is another way to break things free. I tried just threading the new hose on to the fitting but it's keyed and naturally...

Frozen Brake Line Fitting
Author: Trey