Just a fast question - do they take the same 'slot' as lvl II skills, or one slot higher? I'm planning my char and it's kinda hard to do so w/o that knowledge
Thx in advance

I'm not sure if this is 100% of the time but here's my experience:

My rare BOs have skills that cannot be taught via the powerstore. Example:
The power store has Viral Matrix 2 which is a COMMANDER level skill. One rare BO of mine has Viral Matrix 3 which can take 2's place.

My guess was that it's dependant on the first slot when the skill can be learned:
So, Viral Matrix I is learned at slot III, Viral Matrix II is slot IV, so Viral Matrix III have to be at the same slot.
BUT
Science team I is learned at slot I, Science team II is slot II, so Science team III takes slot III.

Does that makes sense?

It does, and appears to be how it works as far as I can tell.