Going back in recent history, the tracks through the tunnel to Snow Hill were closed, and trains formerly running through the tunnel were diverted to terminate at Moor Street in about 1970, and Snow Hill was closed completely by 1974. For 15 years the tunnel was derelict, until a plan to restore the old Western cross-city railway route for local trains was adopted in 1985.
The tracks were renewed, and new platforms were built next to Moor Street station, which was abandoned when the new cross-city service recommenced in about 1987. It stood for ten years as a derelict shell until the Bull Ring rerdevelopment scheme was mooted in the late 1990s.
I believe most of the money for the restoration of Moor Street Station came from the redevelopers of the Bull Ring site who were encouraged to make their contribution on the grounds it would add to the appeal of the site.
Most of the original concourse was brought back into use, to provide access to the new platforms which have been considerably improved. But track connections to the old platforms have still not been carried out.
From the time the restoration was complete the property has been owned by Network Rail, and the station run by Chiltern Railways. It is regularly served by local services now run by London Midland (formerly Central Trains), which is subsidised by Centro, the West Midlands public transport authority. Chiltern Railways run a half-hourly service, usually from Snow Hill through to London Marylebone over the former Great Western route through Leamington, Banbury and High Wycombe.
There is an excellent web site on West Midland railway history.
Peter