A and B are inverting and non inverting Driver outputs and Receiver inputs. The absolute maximum rating of A,B is -8V to 13V. Therefore the signals on these lines need to be less than this maximum rating. Datasheet doesn't say anything about the scenario in title and we have no measured data about it. However, seeing the block diagram it looks like that the device will not be damaged having the signals available on the the pins A, B while Vcc is off. If you have concerns you should test a prototype first to verify all the possible corners according to your design specification.