I've just looked up the comander bonuses of FOC in the XML... Here's the list:
Empire:
Piett - 25% health for all ships and 25% additional health for ISDs
Thrawn - 20% health, 10% damage, 10% shield, 10% armor and 10% movement speed bonus
Emperor Palpatine - 25% health on land and in space, addtitionally 25% shields in space
Veers - 25% health on land (though his icon doesn't glow - strange)
Grand Moff Tarkin - 25% health and 10% on about everything else (damage, shields, armor and movement speed), sapce only
Rebellion:
Mon Mothma - 25% health in space (still)
Ackbar - 25% health for all ships
Garn Bel Iblis - 10% health and damage on land, 5% health and damage in space
Rogue Squadron - 25% health for all ships
Yoda - 25% damage bonus in space. Strangely I haven't found a bonus for land units...
Zann Consortium:
Tyber Zann - 20% health and 10% movement speed in space
Urai Fen - again haven't found anything despite a blinking icon in land combat...
It's possible that the data about the original heroes of EAW is not up-to-date, since they get a file of their own (which could be just copied from EAW), however I haven't been able to find anything newer yet...