Do Time Stories combats during travel between Locations use up Time Units?
As you said the rules don't seem to cover these exact scenarios, but the way I interpreted the rules I assume that any test or action that causes me to roll the dice costs a TU unless the text specifically says it doesn't cost any TU.  My main reason for thinking this is that the base rules do specify that all tests cost a TU, and some expansions do have cards with text specifying that a test can be performed without spending TU.