Man, I just went back and tried the trade again on ESPN trade checker and once again, it failed. It has to be that Real GM is taking the Knicks trade exception into consideration and ESPN isn't. In any event, if the trade is possible, then I'd trade Jimmer straight up for Shumpert. The problem is, I thought the Knicks were looking for frontcourt help.
Hmm. This is getting curious. The trade would work straight up under the 150% + 100K rule...but the problem is that that rule only applies to non-taxpayer teams, and the Knicks are over the tax. That means they are restricted to 125% + 100K, and the trade no longer works with that restriction. The Knicks' trade exception is only for $850K, not enough to trade for Jimmer alone. And the trade exception can't be combined with the 125% + 100K rule, not allowed.
So it looks like ESPN is right and RealGM is wrong.
However, there is a way to make this trade work, if the Knicks are really into it. If we kick in Hamady N'Diaye and the Knicks kick in Cole Aldrich (both guys make the same amount, both unguaranteed), then the increase in total salary brings the 125% + 100K rule into play - we'd be clear by a whole $11K! But, those guys (Aldrich and N'Diaye) can't be traded until December 15th.