[PK]

It's an art, not a science -- the "correct" answer will always be up to the GM. No exceptions.

I find this one question is key:

When I describe what this spell does, do I find myself referencing specific GURPS advantages and/or disadvantages that the subject gains?

In my opinion, Haste can only be meaningfully phrased as "The subject gains ATR 1" or some combination of words that effectively mean the same thing. So it has Altered Traits. But Intercom seems best described as "The subjects can hear each other's thoughts." So it doesn't. If you think it should, and you're the GM, then you're right and now it requires it.