In message
,
Chris writes

On 23 Nov, 15:13, Roland Perry wrote:

Or is there some microscopic wriggle-room that decides a Heathrow
Connect train is "overground" as far as H&H, but then becomes something
else (surely not "underground, wombling free") thereafter?

There is - from Hayes & Harlington, the service is operated privately
by BAA, not an ATOC company.

I don't think being a member (or not) of ATOC is the reason. After all,
people will not be able to use Oyster on the Olympic Javelin, which is
to be run by SouthEastern, an ATOC company.

I guess a decision was made to exclude certain premium services of this
kind.
--
Paul Terry