Believe it or not.
I got both of my 2006 GTs to work off one remote fob.
A couple of weeks ago I got a used fob cheap for the white car I was about to buy.
I programmed it on my blue car to see if it worked.
It worked fine.
When I got my white car the other week I programmed it for that car as intended.
It now will work on either car.
The white car ended up having both original remotes that only open it.
The blue car still has the 2 remotes which only work with that one.
But, I have a 5th remote which opens both cars at once.
Of course, if I am out anywhere it opens the car that I have with me.

 

SUGGESTION:
if youve got kids, cut the contacts out for the panic button...last year I had 3 mustangs and the minivan all on one, my 2 yr old woke up in the middle of the night and went downstairs(yikes!) found my keys and the little red button...I woke up to a serenade from all the horns blaring- one outside, two in different garages...I grabbed the keys, hit the button, one goes off, two on, etc...had to run out in the rain and do the drivers door key lock/unlock twice(important to remember that works to kill the alarm) to shut them all off...
my neighbors saw me before calling the cops luckily, and actually kinda chuckled when they found out our 2 yr old did it, but I'm sure they wouldnt be laughing if it happened again

other drawback- my wife goes to the store, next day I go down the driveway and my trunks bouncing up...handy if youve got several fords, but can be a pain too

 

Of course, being old...
All my kids are grown and gone.

 

Nice. Last I remember, you needed an IDS to program the fobs. I'm fairly sure that each fob can store two key codes.

 

on the fords each fob just has one code, the car can be taught to recognize several codes...I think its like 4 keyless fobs and 8 PATS keys per car? (its in the owners manual)

 

That makes sense.
I assumed it was the other way around and the fob wouldn't interact with the 1st car when I did the re-programming sequence.

 

Yep. If they are the same part numbers, they can be programmed for more than 1 car. Which is a scary thought when you bring your car to be serviced huh? I was a GM tech for years and I have a box full of old remotes. I could have easily found one that could be programmed to any customer vehicle I chose. Just something to keep in back of your mind.

 

it's neat, but I'd never do it. No reason to. If both cars are in your garage, you go to unlock one, it does both, then you have to lock that one, and it locks both. Seems more trouble than worth, especially since there are two separate keys.

 

Ah... you make good sense.
But for me, I have reasons.
It makes my life easier.
It is now on the key chain for my truck.
I can get in both cars to get things without the keys. Then I just lock both when I am finished, no problem there.
Also, I want a remote that works for whichever car I happen to take.
This is a spare remote to open the car I have out and no where near my garage.
I can give it to my passenger if we split up so they can get into the car and get stuff or lock stuff in the trunk.
In the garage, I can open both trunks simultaneously to move my car show cleaning stuff from one to another.