There’s a lot of misconceptions here and fundamental misunderstanding of the law.
Recording is not legal where someone has a reasonable expectation of privacy, ie in a private home or changing room. The ownership of the land in relation to to the recorder isn’t the defining aspect. Railway stations, trains, shopping centres, fields and meadows are public spaces for the purpose of privacy.
You can be asked to leave a shopping centre for any reason (recording video or otherwise) by the premises owner withdrawing implied right to enter, with very little recourse.
You could also be asked to leave the railway premises theoretically, although the person doing so would need to be duly authorised by the company and be supported in that - which may be the first hurdle if they are acting outside of their remit.
Further, there is nothing in the contract of a ticket purchase (NRCoC) that prohibits filming, much like say the easyJet conditions of carriage (interestingly some carriers like American Airlines do specifically prohibit this).
As a contract has been entered by the passenger for travel, the TOC is then in breach of contract if they ask the passenger to leave - the remedy may be a refund or costs such as a taxi to the final destination.
I don’t see anything in the byelaws that prohibits filming if you are continuing about your railway business (entering, exiting, changing trains etc), so there is no byelaw justification for evicting the passenger not stopping them filming.
On that basis I can only see it as a civil issue of breach of contract or at worst trespass, if indeed the original request to vacate was supported by the reverent ToC.
If you’re confident of a valid ticket it would probably be a profitable exercise testing this in resulting costs and/or compensation.
That said this hypothetical scenario is kind-of irrelevant, on the ground if you have a valid ticket and are polite you are extremely unlikely to encounter any issue in the long run as recording a situation will just show up any miscreant member of staff and embarrass the ToC into submission through the footage of such transgression.
Albeit quite old now a case in point... valid 1st ticket on the HEX boarding at T5, guard believed it was not valid so I started recording him as passively as possible, he got quite irate quite quickly and insisted I leave the train at T123 and when I refused he said BTP would be meeting the train at PAD. They indeed were waiting at PAD, I showed them my ticket and demonstrated why it was valid, offered my name and address but said I would otherwise be on my way - they were completely disinterested and recommended the train manager take it up with his control and let me on my way. Eventually received a free carnet of tickets by way of apology from HEX.