Forgive me for not knowing the correct info,but I thought any new or replacement foot bridges had to be wheel chair compliant.
Possibly under the Equality Act 2010? Though I think that perhaps doesn't apply to railway structures. Anyway, at the moment they seem to be dealing with it by making a promise:
The design of the footbridge also accommodates the future installation of lifts, which subject to future funding being approved, will enable the footbridge to provide connectivity to the station and town for all users.