If plans succeed, Chiltern Railways would provide half-hourly weekday services between Aston Rowant and Marylebone station in London.
At present, a preservation association runs weekend steam and diesel trains between Princes Risborough in Buckinghamshire and Chinnor in Oxfordshire.
The association's deal with Chiltern would involve Chiltern's holding company, M40 Trains, extending the track between Chinnor and Aston Rowant.
Chiltern could then operate 50-minute journeys from Aston Rowant to Marylebone via Princes Risborough and High Wycombe, while the association would have an extended line to operate on at weekends.
"Trains could be running in two to three years," said a Chiltern spokeswoman.
Adrian Shooter, Chiltern's managing director added: "We believe this innovative scheme would offer real customer benefits to local people, both in terms of providing a service that has not been available for the last 40 years and in terms of helping reduce traffic on our crowded motorways."