Most single-din HU's will fit in other single-din cages, but the locking tabs are different w/ different brands. JVC cages have a nutty lock though.
Why would you want to swap cages?
Does your current HU not have a cage and you are looking for one to use?
If so, What vehicle are you looking to install the HU into? Many Metra dash kits offer both Din and ISO mount hardware. If you can use the Metra ISO-brackets to install an HU w/ no Din-cage, you will be fine.