John,
If I may refer you to the Southern website http://www.southernrailway.com/tickets-and-fares/season-tickets/ it states quite clearly
"It may be used at intermediate stations, and on any permitted route, unless a route or any other restrictions are specified on the ticket."
Therefore it would appear that season tickets are not specific between point A and B, as you suggest.
The ATOC in their routing guide have Clapham Junction, Streatham Hill, Tulse Hill and London Bridge all within map LB which would suggest that a season ticket from Clapham Junction to London Bridge should be valid to travel from Tulse Hill ref:
http://www.atoc.org/about-atoc/rail-settlement-plan/routeing-guide
Can you confirm if a season ticket from Clapham Junction to London Bridge can be used for a journey from Tulse Hill to London Bridge?
Dear Mr XXX
Thank you for contacting Southern about the validity of your season ticket to travel from Tulse Hill.
Unless the season ticket says it can only be used on a specific Train Company, it is valid on all Train Company services on the route and within the zones for which the ticket is issued.
Having investigated the routing guiselines I can confirm it will be possible for you to travel from Tulse Hill, as it is located on the relevant routing map.
If you have any further queries or requests you wish to make, please contact our customer services team on 08451 27 29 20, where our Bristol based agents will be more than happy to assist and support in any way we can.
We appreciate you taking the time to contact us.
Kind regards
Marcin Balawender
Southern Customer Services
Telephone: 08451 27 29 20
Fax: 08451 27 29 30
E-mail: comments@southernrailway.com
I wonder whether the routeing guide or the routeing on the ticket will be changed. It would be quite easy to make the ticket route Vauxhall/Battersea Park. We shall see.
Since there's a half-hourly direct service between CLJ and LBG (via Crystal Palace), that would seem a bit draconian!
There could though be an easement to "relax the rules for certain routes" so as to "improve connections" by forbidding it.
I'm not sure that the direct service would be of use to the OP though.
I don't think they can do that; it makes a hash of the trains from MKC-KPA-SRS.