The Mayor has announced that First Great Western will be the fifth train company to roll out Oyster on all its London services:
Thousands more passengers using these routes will be able to enjoy the greater convenience and speed of Oyster at stations from West Drayton and Greenford into Paddington. Zonal fares the equivalent of those on the Tube will apply for journeys from these stations.Since April 20th they've accepted it on trains between Paddington, Ealing Broadway and Greenford, but at no other stations. Oddly there's no mention of Heathrow Connect, which is a surprise given much of the local service on this route is supplied by trains with that name on the side*. I shall enquire.
Boris also promises a summit with the five remaining companies to get their agreements sorted out. Apart from South West Trains, none have legally committed to accepting PAYG any time soon. Southeastern do publicly "hope" to accept it by January 2009.
Update: Just had confirmation that, as expected, this applies to Heathrow Connect as far as Hayes & Harlington, but not to Heathrow.
* Heathrow Connect isn't a company, it's the manifestation of an agreement between BAA/Heathrow Express, First Great Western and various government bodies, and has a suitably byzantine operating structure