Can I use the same controller for multiple cars?
 

If I get another 27MHz (or 49 MHz) car only, can I use my original transmitter for it, or are they tuned for one car only somehow?

Same brand controllers will work with same brand cars (as long as the frequency is the same).

So, A Tomy Bit Char-G controller set for 27MHz will work with ANY Tomy Bit Char-G car set for 27MHz.

That's for the regular controllers anyway...I can't verify that's true with the Booster Controller/Cars