Wow,
Thanks everyone; I was really surprised that the answer wasn't simply "of course not!" - many thanks for the interest and effort all responders have shown. I always thought it was a fairly safe assumption that in its "little more than a plastic box" mode, a CM15 tranceives one way only - As Puck points out, the alternative sounds more dangerous than useful.
Actually, and taking on board all the comments so far, it might be worth considering the question in a slightly different way:
"Are there any circumstances in which a CM15 which has no "send RF" commands stored in EEPROM, and with nothing plugged into its USB interface, will transmit a command on RF"
As I've sparked some interest, I will post details of the observations that led me to ask the question, but as said I already have empirical solutions, so the only value in exploring it further is pure curiosity - the desire not only to resolve, but also to explain. I'll try and post in the next couple of days - although the situation is actually extremely simple, there's a body of evidence gathered from investigating various options around it, which I need to find a couple of hours to present properly in a post.
Cheers to all,
Alan