It seems to depend on which website you look at:
Airframes.org = HMNY
icao.int = HMNY
caa.co.uk (G-INFO) = EV97
Well not really.
For a start, G-INFO doesn't claim to show ICAO codes (EV97 is simply the CAA's generic description for the Eurostar and teamEurostar).
And all that the ICAO site will tell you is that HMNY is a valid code (albeit for the EV-97VLA variant), it doesn't track aircraft by serial number.
Airframes.org has simply got it wrong, I'm afraid.
Edit: I've just checked, and GAS says HMNY too, so alas they are equally incorrect.