Evasion, like the 3e sneak attack and Heart of Fury mode, require code support in the actual engine. There's probably some poking around you can do with mods, but not a lot--e.g. David and I manged to get evasion working for IWD-in-BG2, but only through a lot of hacks.
However, since it's a shared code base it's entirely doable to see this code turn up in BGEE/BGIIEE in the future. The problem is that it's a lower priority than, say, bug fixing, and testing code merges for regressions is a non-trivial QA exercise. I want it there, and personally I think it will be--the problem is that there's no way I could say that for sure, and certainly not attached to any kind of a timeline. Few things would get me into more trouble than for someone to take this as 'Beamdog confirms...'
At worst, if Beamdog stopped doing anything today, maybe someday we'd see a Baldurs Gate 2 in IWDEE conversion mod. It would be a funny completion to the circle to this project of IWD in BG2.