Do you not have fuses in the plugs for your 'expensive' devices?
Normal fuses in plugs tend to be relatively slow acting*, and from what I understand the train in motion can (if the carriage itself hasn't got filtering to the sockets) send surges through the socket as the power pick up passes over joints in the supply rail or cabling. They do little against momentary surges of the sort you get in such situations if my memory serves.
Of course the charger is more likely to be damaged than the phone, if properly designed and it meets the safety standards.
But the main reason I wouldn't plug a mobile phone into a socket marked "for cleaners use only" or similar is that I don't think the rules don't apply to me, and I have what sometimes seems to be an unusual ability to keep on breathing, thinking and coping without a mobile phone in my hand constantly.
Which tends to mean if the phone runs out of juice, or runs low I'm not desperately looking round for somewhere to plug my hand held tasp in to be recharged.
I've never grasped how/why people get so addicted to their mobiles that they can't put the things down for a few minutes when the situation is inappropriate for their use, and seem to panic when they run out of charge.
*They're intended to cope with things like the momentary surge when you turn on an older style electric motor without blowing (such as your vacuum cleaner, or freezer) and from memory are more current related, not necessarily voltage (or at least not low and quick enough to stop the over voltage damaging something else). One of the reasons a lot of devices may also have an internal "fast blow" fuse, as the plug fuse may not blow fast enough to protect internal components in the event of a fault.
