As for your bad actor: what would he pressurize your lines with? An air compressor? He'd have to dig up the lines or disconnect them first and gas from the line would likely escape in quantities large enough to discourage such tricks.
Just like in theory you could disconnect the mains from a house and then send a high voltage pulse down the feed lines, in practice pranksters and miscreants tend to avoid doing stuff that might get them killed instead.
On the gas meter on my house anyway, the underground pipe mates at a valve. It doesn't seem hard or particularly dangerous to shut that valve off, disconnect the meter, connect whatever, then open the valve again.
Anyway, if you want to destroy someone's house there are much quicker, less obvious and easier ways to do so.