I found this using the Search function, and thought I'd give it a bump...

I know it's not technically an airline, but FT does include Amtrak, hotels and cars, and the Eurostar Frequent Traveller programme is disturbingly like an airline one... (and so is the passenger experience - minimum check in times, upgrades, lounges, delays, compensation, etc, etc). Anyway, it would be a good idea to start such a forum, especially as they carry more pax between LON-PAR and LON-BRU than all the airlines put together.

Incidentally, I believe UA MP have now formally parted ways with Eurostar, although judging by the vast number of "you-must-be-kiddings" whenever I tried to earn MP miles on Eurostar, you'd never have thought they were ever partners in the first place...