IB screwed me over and I tried getting into Fidelity to buy the same asset before and they said IRAs *could not* use foreign currency (even if just swapping to a SEK-denominated asset) and they could not trade COINXBT.
There is a fellow on SeekingAlpha who recently was able to do the trade in an IRA at Fidelity:
https://seekingalpha.com/article/4137459-bitcoin-altcoins-missing-wave?ifp=0&v=1516625100 (toward bottom, posts by Jim Craddock this afternoon)