the top part of the card (requiring a shuttle) says:

"you may immediately retreat. if you do, cancel the imperial tactic card"

my questions pertaining to this card are:

1. Do I need a leader in the system to preform this (i would rule no).
2. If i retreat, do I have to take all my forces? can I leave ground units as normal? (i would rule that i can leave ground units)
3. If I have already retreated once (normally) can I play this card's action and retreat again(yes?)? what if is the other way around, can I retreat again after I have played this card(maybe?)?

Cards only break the rules they say they break. So you still need a leader, can't retreat to places with enemy units etc.

the only difference is you do you do it immediately. That's the only rule change.

So

1.yes

2. No

3. You can't retreat into a combat, so I don't see how you could have multiple retreats in the same activation.

During a ground combat step, let's say the Empire has some Tie Strikers left in space and plays Air superiority (Cancel the Rebel tactic card), while the rebel player still have a rebel transport in space and plays Escape plan ( You may immediately retreat. If you do, cancel the Imperial tactic card), are both cards canceled out resulting in the rebel player not able to escape?

21 minutes ago, IanSolo_FFG said:

During a ground combat step, let's say the Empire has some Tie Strikers left in space and plays Air superiority (Cancel the Rebel tactic card), while the rebel player still have a rebel transport in space and plays Escape plan ( You may immediately retreat. If you do, cancel the Imperial tactic card), are both cards canceled out resulting in the rebel player not able to escape?

It depends on who's activation is (the current player). The rule says:

"Starting with the current player, each player chooses and resolves the top or bottom ability of his tactic card."

So the current players tactic card will resolve first. If it is the Rebel player, then you cancel the imperial tactic card and retreat. But if the current player is the imperial, then it cancels the rebel tactic card before it gets a chance to resolve and they don't retreat.

57 minutes ago, IanSolo_FFG said:

During a ground combat step, let's say the Empire has some Tie Strikers left in space and plays Air superiority (Cancel the Rebel tactic card), while the rebel player still have a rebel transport in space and plays Escape plan ( You may immediately retreat. If you do, cancel the Imperial tactic card), are both cards canceled out resulting in the rebel player not able to escape?

32 minutes ago, Lemmiwinks86 said:

It depends on who's activation is (the current player). The rule says:

"Starting with the current player, each player chooses and resolves the top or bottom ability of his tactic card."

So the current players tactic card will resolve first. If it is the Rebel player, then you cancel the imperial tactic card and retreat. But if the current player is the imperial, then it cancels the rebel tactic card before it gets a chance to resolve and they don't retreat.

I think that is questionable. Under the Canceling Cards section of the expansion rules it says, "When a player's tactic card is CANCELED, he cannot resolve any of the abilities on it. Although the current player usually resolves his tactic card first, if the defender's card uses the word CANCEL, the defender resolves his card first."

So really if we are going by activation order the second part of the rule implies that the rebels only can cancel and retreat as Lemminks86 says if they are the defenders.

I think the spirit of the rules would be that both cards are canceled and nothing happens.

33 minutes ago, NukeMaster said:

I think that is questionable. Under the Canceling Cards section of the expansion rules it says, "When a player's tactic card is CANCELED, he cannot resolve any of the abilities on it. Although the current player usually resolves his tactic card first, if the defender's card uses the word CANCEL, the defender resolves his card first."

So really if we are going by activation order the second part of the rule implies that the rebels only can cancel and retreat as Lemminks86 says if they are the defenders.

I think the spirit of the rules would be that both cards are canceled and nothing happens.

You're right, my line of thinking was that if both have the word cancel then it will be resolved as usual (with the current player first), but if we go by the rule as written, then if the defender uses a tactic card that have the word "cancel", his tactic card will resolve first regardless if the attacker also used a card like that, as we have nothing written for that case, and the only rule we have is referring to the defender:

"Although the current player usually resolves his tactic card first, if the defender’s card uses the word cancel, the defender resolves his card first."