GSM notes from conversation with Telefonica for IoT Launchpad.
DHD20150901 (10:00--10:45)

For 2G, regarded as pretty much mature or even EOL, most equipment is
interchangeable.

(Note that 2G *and* 3G may get turned off within the next 10 years.)

2G offers circuit and packet switched, but for Launchpad purposes packet
switched is the only form that is of interest,

There are varieties of SIM that can attach with preference to one operator's
towers or be more agnostic, but for LP initial deployment we can probably live
with any flavour.