Colin Rosenstiel wrote:

It's got some local bus service attributes (it provides the main
Cambridge-St Neots bus service these days) but is treated as a coach
service at our end.

In what way, other than it doesn't (I think) take standing pax? (It
used to, it's just that the current coaches don't have anything to hold
onto, being ex-National Express). I'm still pretty sure I have seen
under-16s on it on several occasions.

Pretty sure, yes. Clearly now it just tries to send you via London, even
though it is quicker and almost as frequent to use Central.

Thetrainline.com is still doing it now. Try a return from Birmingham to
Cambridge on 2 October around 16:30:

Interesting - TTL and NREKB appear to use different logic, odd given
that they're the same software.

Notably, though, while it does present the bus option it also presents
the via-London train service. Many people (including me) try to avoid
travel via London in the evening peak, as it isn't fun.

Press "earlier trains" and the direct service is there, incidentally.
It doesn't usually show trains before the specified time (though
sometimes it does, try 1615 and the 1612 is shown - perhaps it's a
5-minute threshold?)

Return journey: Monday 2 October 2006
Station Arr Dep Travel by Service Provider
BIRMINGHAM NEW STREET 16:30 Train VIRGIN TRAINS
MILTON KEYNES CENTRAL 17:22 17:40 Bus VIRGIN TRAINS
CAMBRIDGE BUS STATION 20:00

Note the claimed provider of the X5 service.

I agree this is misleading, if only from a ticketing point of view.
(Any P tickets are NOT valid on the X5 - there is a specific
destination and/or route). It's in as VT-operated because they added
it to the database.

They are evil, trying to pass buses off as trains.

Hardly.

Neil