Are the TOCs really competing with each other for staff to any significant level? Furthermore there are of course the unions, which probably have a greater effect on pay.
Don't forget that, like most things, prices and pay are determined by the demand at the margins. So the level of competition between TOCs for a particular set of skills depends on the type of skills and the size of the pool of appropriate staff.
This, I suppose, a long-winded way of saying that train drivers — because of the set of aptitudes needed for periods of concentration, remembering details of rolling stock and routes and a book's worth of operating procedures — are more likely to be able to 'vote with their feet' than those with more generic skills. The costs of training also plays a rôle, it can be economically more advantageous for TOC 'A' to offer higher pay to an already experienced driver from TOC 'B' than train one
ab initio. Here the risk that some candidates may drop out before completing the course does not fall on TOC 'A' which can then pass on some of its savings to its new driver.
This also explains why customer facing staff are not as highly paid as train drivers — the skills needed are more akin to those sought by speciality shops in the High Street, of which there are many.
Unions certainly do have an effect on pay scales but this is limited in time. Over a period of several years changes in general economic activity tend to outweigh the effects of any individual pay deal.
Given a lot of grades are going to see retirements in excess of recruitment, a decent salary is going to be needed to keep people there rather than leaving the industry, retiring, or becoming consultants.
I wouldn't bet on it, the forces of economics are inexorable.
