Yes. A short little Bluetooth dongle was included with my B2. I don't know for sure if that is just for receiving Bluetooth signals, or if it's intended for transmitting as well. Brennan says on its website that although the Bluetooth transmit capability has been left in, it is not officially supported.
You should try it with whatever dongle you have. If it doesn't work with your Bluetooth speaker, there are alternatives. Some of the folks here have had good performance with a separate Bluetooth transmitter into which they connect either the B2's analog or digital output.
Another option is to get the Bluetooth core update for the B2's Raspberry Pi operating system from the Latest Software page on the Brennan website and build yourself a new SD card. The instructions are on the Techy Stuff page.