APCs and Armored Car questions

[J6A]

Do APCs generate wrecks?  The way I read the rules they do.  However, it makes for an interesting situation.   I have APCs and armored cars dueling it out in an assault in town (along with various infantry).  By the time it's done, there may be 3 AFV step losses in the hex.  If they each create a wreck  it seems any remaining APCs, and the armored cars would be stuck there because they can't clear wrecks.

Also, from what I can tell, armored cars cannot be efficient and don't provide the combined arms shift in assault.   Is that correct?