I have a Railking 2-8-0 (had Locosounds) with a PS2 upgrade kit installed. When I was installing the PS2 upgrade kit in my Williams brass 2-8-2 I hooked the 2-8-0 tender to the engine to make sure it would run and it did.
What I'm saying is maybe it CAN be done if both engines were PS2 upgrades.
Now it may not run exactly as it should, because of driver diameter, flywheel size, etc, so I can see where George is coming from. I wouldn't necessarily stick an 0-6-0 tender on a Big Boy.