An overseas train operator could end up running the first significant new railway in London for more than a century.
The competition to run Crossrail services and some stations was launched in March by Transport for London (TfL).
The operators of the Paris Metro, MTR of Hong Kong and Deutsche Bahn have said they are interested in running the line. In contrast, domestic operators including First Group, Stagecoach and National Express have not rushed to declare their interest.
The competition comes at a time when the United Kingdom's rail franchising system is under strain after an embarrassing failure over the award of a 10-year franchise to run the prestigious west coast London to Glasgow line.
Sir Richard Branson's rail group Virgin Trains lost the competition for the West Coast contract to First Group last summer but was then reinstated as operator after it was discovered the department of transport got its sums wrong and the first result was set aside.
The fiasco and subsequent inquiries have led to delays in awarding other rail contracts and there are now 10 mainline franchises coming up for tender over four years.
RATP, the French group that runs the Paris Metro, has declared its intent by appointing Elaine Holt, a British rail-industry veteran, as its bid director for Crossrail, attracting her from National Express. Ms Holt previously worked for First Group and was parachuted in by the UK government to run the bankrupt East Coast Main Line when it was renationalised.
MTR is another serious rival. It already co-runs the London overground train network, which is now one of the UK's most reliable railways. Jay Walder, an American who became the chief executive of MTR last year, knows Crossrail well as he worked with London's previous mayor, Ken Livingstone, and was a finance and planning chief at TfL.
"We believe our experience of establishing and operating world-class metros in major cities throughout the world means we have the type of expertise a Crossrail operator would need," MTR says.
MTR confirmed it would be bidding solo for Crossrail and not with Arriva - its partner on London overground services. Arriva, which is now owned by Deutsche Bahn, has confirmed it will also bid.
TfL says it wants an operator in place from May 2015 to run the trains as well as many of the stations along the route, which initially will open then on the existing line between Liverpool Street and Shenfield in Essex.
Services on new lines through Canary Wharf, the City and the West End are due to open in late 2018, with Crossrail fully in business out to Heathrow and Maidenhead in Berkshire by 2019.