You can charge batteries (and other EU storage items) and use RP2 retrievers with ender chests to charge them up, move them through the chests, then discharge them into an EU storage block in your base.
This design for the charging-up end is simple and effective, and can be scaled up with a bit of work to multiple MFSUs:
+ = pneumatic tube
M = MFSU
R = Retriever
T = Timer
E = Ender Chest
The MFSU is one block below, with a tube on top of it.
Have one of the Retriever pull empty from the chest and put it in the MFSU, the other would pull full Lapotron from the MFSU and put it back in the chest. Set the timer to 5s or something.
The discharging end would be the same, but with the pneumatic tubes leading to the bottom of the collecting MFSU instead of the top, and the retrievers' sorting items reversed so that full go into the MFSU and empty go back into the chest.
Alternatively, I believe minecarts can travel through Mystcraft crystal frames, and there is an Energy Cart (from Railcraft) that can store EU. That would be another method, though I haven't tried it yet to confirm. I think the storage items method is likely faster and more scalable, though.