Since the ability to hide/display headers is a client (isql in this case) setting, ASE would need some means of sending a signal to the client that says to override the client's show/hide header setting. ("Duh, Mark!" ?)
I'm not aware of any such ASE command, and I don't see any (obvious) commands in the latest/greatest ASE commands reference manual [ ASE 16.0 SP02 PL04 Reference Manual : Commands ]
