Yes, the NXU-2B will work with its predecessor units just like connecting, for example, two NXU-2A's. You will not, however, need the audio crossover adapter to connect a JPS interface cable to the unit.
If you have a cable that connects directly to the NXU-2/A, you will need to rewire it to use it with the NXU-2B. Please see the user manuals for more information.