From my experience with Bluetooth printers, it usually means that they are Bluetooth capable and require a special Bluetooth adapter (made by the manufacturer) attached to them to make them work via Bluetooth. If that condition is met, or if the printer truly has Bluetooth built in, you should be able to access it with any Bluetooth enabled computer. As far as I know, you cannot join a WiFi network via Bluetooth as the technologies are not the same (unless there are Bluetooth routers/access points that I'm not aware of). You can however connect a Bluetooth printer to a networked attached computer and share it over the network that way, but the host computer needs to remain online at all times.
Second, as was mentioned before, any functions other than printing for multi-function printers attached to the TC/AEBS/AEX via USB are not supported. You need to connect a network MFP to your base station, either with an ethernet cable or via WiFi, for you to use the scanning function. Or you can connect the printer via USB to a host computer and share it on your network (again, the host computer needs to remain on).