With actual BlackBerry devices, the PIN is hard coded to the device.
Your BBID is tied to you. So, when you log into your BBID, it gets linked to the current device you are using.
When someone sends you a message, it goes to the device you are currently using. If you change devices, the messages follow you, based on your BBID.
PIN messages are messages sent to a specific PIN, irregardless of who is using the device. There is no telling who gets the message, since it was sent to a device, not a person.
I just switched devices this weekend (Note 2 to a Note 3). When I signed on to BBM, it gave me a new PIN number. So it seems that even the Android version will follow the same philosophy.