Here's another option for hydraulic removal.
Install a grease fitting somewhere and pump it full. It might swell the outer sleeve and it WILL definitely force lube into the joint.
Turn the entire fork into a hydraulic cylinder. (You're going to clean it out, anyway, right?)
sparkwizard is right, the hydraulic pressure that the grease gun exerts thru the grease fitting can really put a lot of pressure on the fork.
Use a long lever hand grease gun, not the pistol lever type.
Let the fork assembly, grease gun, grease tubes all lay out in the hot sun for a couple of hours before attempting this.
Go back and forth between both forks, let it sit for a 1/2hr go back and exert a little more grease pressure and just maybe, you will get lucky!
You may waste grease and will have a clean up job afterwards but it may be worth it.
Note: Not responsible for anything that may occur, try at your own risk.