McG,
The Eurotrams are as you say fundamentally TGVs, but they are heavily engineered compared to the older TGVs (I don't know how they compare to the modern TGVs- remember the TGVs have been evolving for some years now).
The thing is that the TGVs don't go through the tunnel, which is where the snow was melting, The snow didn't seem to cause a problem, but the melted snow (water!) did.
Although there are possibilities that they aren't being truthful, if you believe the Met Office...