As per title. What's odd, is that they can be used to craft other IC2 items that require wood (Battboxes, LV Transformers, etc)

This may be an IC2 error. I'm not entirely sure how the Forge dictionary for wood works, but if other recipes are working fine, that may mean they've forgotten to properly set the treetap to support it on their end. I'd suggest sending a report to them as well, just in case.

Per Scott in the EBXL thread earlier today:

All of our wood is in the ore dictionary. The ore dictionary requires two things: Mods needs to make their items available via the ore dictionary. Then...the mods must use ore dictionary recipes. Some mods choose not to use the ore dictionary for their recipes...this is the case with IC2 which was using it and changed back to not using it. Other mods, like Railcraft and Forestry, use ore dictionary recipes and therefore our items work in their recipes.

This is why our wood is not working. It is something that IC2 will have to start using again.

We add no plank recipes for IC2 items. All of that is allowed by the IC2 implementation.

@brknsoul Everyone above is correct. I spoke to @richardg867 of the IC2 team a few days ago about this and he said that IC2 had chosen not to have an Ore Dictionary recipe for tree taps. They had one, but RichardG said that some of their users had a complaint, but in all honesty I didn't understand the problem. I have referenced him here in hopes that he can shed some light on the problem.

So, I'll add it back in for our planks.

Ok, thanks.. It's just a bit odd that I can use EBXL Planks for Battboxes and LV Transformers, but not Treetaps. :-P

I agree...and I cannot fathom why they did it, but they intentionally chose not to use the OreDict for this. 😣