Sort of*, and no in my experience.Does Euston have free WiFi and does it extend to the platform areas? in other words, if I'm in a train that doesn't have WiFi, can I get a signal from the station WiFi?
Two points:
Not many trains at Euston are without WiFi - just the Overground, a couple of LM ones and the Sleeper services! Obviously Virgin have WiFi (chargeable in Standard) and LM are rolling out WiFi to the 350s (and 323s, but not relevant here).
It probably depends on the platform! I have been on a 350 before the WiFi was installed and picked up the station WiFi somewhere on platforms 8-11, but I guess at the far end of platform 1 maybe not.