Travel mode effect on fatigue recovery?

[dukemat]

Correct.
As long as the unit isn't Disrupted, moves, fires or is fired upon, it'll recover fatigue.
Proximity to HQs is irrelevant as well, that only comes into play with Disruption recovery.

being "disrupted" does not prevent fatigue recovery. no mention of being disrupted in the rules.

Units that are disrupted will recover fatigue provided the unit must not move,
fire, assault, be fired upon, or be assaulted for a complete game turn. It must
also not be Digging-In, building a bridge, or be in a minefield. 
There is a nominal rest value determined by Parameter Data (see the Parameter Data
Dialog in the Main Program). During night turns, this value is doubled. Further
modifiers may apply to this value based on Optional Rules described in the
Main Program. The Fatigue recovery a unit receives is then calculated as a
random value between 0 and twice the rest value. The number of units that
recovery Fatigue are reported in the Command Dialog of the Main Program.
Nominal Fatigue recovery also applies to air units.