Just to be picky: The aqusition is not automatically lost by changing (T)CA, as Keith writes in his first post. You can change you CA and keep aquisition as long as you fire on the aquired target that phase.
This can be useful if the target (and the aquisition counter) moves outside CA, or if it is exactly on a hex grain, and you want the TCA to change to the other CA that includes this hex grain.