Is Bluetooth Communication Possible Without Pairing?
Yeah, it's entirely possible. I commented on this previously and have since looked into it further. You can have the triggering Bluetooth device send the activation signal through its friendly name. 

The friendly name is the human-readable name that appears in the the list when you search for a Bluetooth device to pair with. The speed at which this activates depends on how quickly the receiving device polls for friendly names. You haven't mentioned what type of receiving device you're using but I found this PDF (Pg.35) detailing the process for updating the friendly names of in-range Bluetooth devices. 

You can poll for friendly names as often as you require. If your triggering device changes its friendly name to the activation code, abc123, then the receiving device will be able to see that name without pairing and activate whatever task you're attempting to perform. This also allows you to have a multitude of activation codes, I think you can get up to 248 bytes for the friendly Bluetooth name.

You may also look into intentionally opening yourself up to Bluejacking. I'm not familiar with it, but if security isn't an issue it could work.