It worked for me as well.
It did not work with the liveupdate CNNA 2013.20 in my US nuvi 2555 nor the downloaded CNNA 2013.20.img in my Singapore nuvi 2575.
However, when I tried your method of creating the img file from Mapsource (I did a partial selection to save time for experimentation), CNXA 2013.10 appeared on MyMaps and 'Public Transport' now appears as an option.
Thank you.
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