I asked PlusBus about this (using the contact us email link) - asking in particular about being able to use it at intermediate stations with a rail season ticket
their reply was:
1). You can only buy PLUSBUS tickets for the stations/towns named on your rail season ticket at the origin and destination.
2). You cannot buy PLUSBUS tickets if you hold a Rail Rover or Rail Ranger pass.
I have never had a problem buying a Plusbus ticket for a town at an intermediate station on my season ticket. Presumably either the ticket office staff don't know or don't care (although I think I was the first person to ever buy a Plusbus ticket from them), or the Plusbus helpline are wrong.
Before I bought one for the first time I checked the Plusbus website, and the only thing I could see that specifically stated when you couldn't buy a ticket was -
"11. Can I use PLUSBUS if my train journey is between two stations that are within the same bus zone?
Sorry, no. Your train journey must either start, or finish at a station outside the PLUSBUS town zone (or PTE region)."
In my case the intermediate station is well outside where I am starting the journey.
The other examples could potentially be interpreted in different ways, and didn't specifically cover intermediate stations, for example -
"2. I have already bought my train ticket, can I still buy PLUSBUS for my journey?
Yes, if you take your valid train ticket to any train station ticket office, ask for PLUSBUS for either your origin or destination town. "
Well my 'destination' on that journey is the intermediate station I want to buy the Plusbus ticket for, and my train ticket is valid for a journey to that destination. In fact season tickets are advertised on this very basis, that you can use them as you see fit between the two points named on the tickets.
So
if the Plusbus helpline is correct (and I don't believe they are), they need to put the information in clear unambiguous terms on their website. Then my local station can go back to the situation before of never selling their tickets.
As a aside, one of the reasons why I suspect that there are never any tickets sold for my local town, is that the pricing policy seems very strange.
For example, a Plusbus ticket for Milton Keynes costs £2 a day and covers a vast area of MK and Bletchley, and gives a good saving compared to a normal Arriva day saver of £3.50.
However in my local town, where the Plusbus ticket covers an area about 2 miles in radius and only three bus routes, all of which stop operating before 7pm, the Plusbus ticket still costs £2. However since a single each way on the bus from one side of town to the other is 85p, the only people likely to pay buy a Plusbus ticket are those who can't do maths.