Really interesting to see this development in Europe - especially if it covers more than one type of transport and multiple operators. 

These initiatives are much easier to implement if there is only one operator who can act as "Merchant of Record" for the purposes of processing payment card transactions - as with TfL. 

If there are different franchisees operating bus, rail and other methods, it can be a different story. Especially if operators need to use the same systems and  are expected to support fare capping.