I have a Nuvi 3790, and loaded it with the new City Navigator North America 2013.10 and then installed City Explorer North America 2012.30 to the SD card.
The older City Explorer seems to work with the newer map.
It shows "powered by cityXplorer" in the "Transportation Mode" selection screen.
City Navigator Europe 2013.10 and City Explorer Europe 2012.40 seem to work together too.
Have done no other testing.
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