Having the day off work today, I went for a stroll around Liverpool. I saw one of the vandalised Merseyrail trains at Moorfields around mid-morning, on a service to New Brighton.
Perhaps it was one of the same trains as mentioned by the OP.
First two carriages were fine, but the rear carriage was covered in graffiti for pretty much the length of the whole carriage right up to the windows.
Other people's observations may vary, but as a semi-regular user of Merseyrail over the years I have to say there was a long period when it was very rare to see graffiti on Merseyrail trains. Apart that is from the occasional incident which actually made the local newspapers. I do recall this happened when someone travelled right across the country spraying graffiti on trains and made it as far as Birkenhead.
More recently though (i.e. within the last couple of years) I have seen graffiti from "casual scribblers" which are just names or plain words usually in red paint, e.g. above some of the doors. This stuff usually gets removed fairly quickly it seems.
But since the Open Golf Championship event at Hoylake, I have noticed an increase in what I would describe as stylised monograms, the sort of stuff that consists of many colours and chunky symbols, but looks pretty much unintelligible to the casual observer. That stuff must be a real pain to remove since it covers such a large surface area. Also, Merseyrail have just redone the exteriors on many of their trains, so I guess they won't be too happy about this latest wave.
Still, the problem is nowhere near as bad as other countries as already stated. My last trip on the Rome Metro (which was admittedly over a decade ago), trying to get back to the campsite. Purple graffiti over the entirety of every window of the carriage - just couldn't see out. Didn't know at all where we where. So waited for the doors to open - looked out of the train doorway - all of the station signs had been sprayed too, making them completely unreadable. How we got back I can't remember, we just had to rely on visual clues like surrounding buildings etc.. Thankfully things aren't that bad here just yet.
