Does Omega Ace's ability to disallow dice results being changed prevent the usage of an evade token?

Yes, cause evade token is dice modification. (adding result)

Assuming you mean Omega Leader, yes. The FO's ability prevents all forms of modification by the ship he has TLed, which includes adding results in the form of using an evade token to add an evade result

Omegal Leader (not Ace, he's the 'spend a focus and a lock get all crits' guy) works as follows:

If you have a ship locked, and you're targetting them with an attack or they're targetting you, and THEY try to do the following:

- Add a die result (e.g. evade token effect, Advanced Targetting Computer, the second part of Accuracy COrrector)

- Change a die result (e.g. focus token effect, Poe's ability, autothrusters)

- Reroll a die

Then that fails.

It also prevents the Heavy Laser Cannon from changing its crits back to hits.

It also prevents the Heavy Laser Cannon from changing its crits back to hits.

WHich falls under 'change a die result' yes.

It also prevents the Heavy Laser Cannon from changing its crits back to hits.

WHich falls under 'change a die result' yes.

Yes, but some people tend to overlook this one because it actually hurts Omega Leader, so I thought it was worth specifying.