I recall BG spraying the insides of the gas main in the street where I
lived, about 15 years ago, to reduce leaks. I believe (i.e., I don't
know the details) that this involved pushing a small plastic pipe,
similar to a drain jetter into the mains to spray it. I didn't hear of
any subsequent problems.

It seems it wasn't very effective, since they dug up the street and
replaced the steel/CI mains with MDPE a year or two later. I don't know
if they still use this technique.

It sounds like blarney to me.