It now appears that the gas meter is long-life battery powered, which alays one of my fears, so far so good.
However, the 'phone-home' technology is GPRS, which confirms my fear of possible 'GSM chatter' broadband intereference, or even just interference with TVs and Sound systems. I have very little confidence that BG would be pro-active in resolving any such interference, if it arose.
There is also an in-home network, by which the meters communicate with the GPRS hardware, and with the display unit, which uses 2.4GHz wireless. That probably (thoughts, anybody?) won't interfere with broadband, but does add to all the other GHz clutter from WiFi, DECT phones, wireless keyboards, etc, and I'd not be surprised if some symptoms arose.
I'm as yet unclear about meter-ownership. These are not standard meters, and they must cost more to make. If BG are installing them in their capacity as 'energy supplier', then they mayt well ask for them back rather than pass them on free-of-cost to another supplier.