The bottom-placed Hammers looked set for a first away success of the campaign after Frederic Piquionne and Valon Behrami had put them in command.
But City substitute Jerome and Ridgewell rescued a point for Alex McLeish's side.
Hammers co-owner Sullivan looked on impassively against his former club but at least he was able to witness proceedings at first hand after former Blues chairman David Gold had been banned after comments about the Midlands club.
West Ham looked to have the points in the bag after playing with a confidence that belied their lowly position.
Carlton Cole impressed as the lone striker and his occupying of the City defenders allowed Victor Obinna to find space to exploit.
In contrast Blues struggling for long periods to pose any sort of threat - until they went 2-0 down.
Birmingham, operating with the 4-3-1-2 formation which had been successful against Blackpool in their previous home game, found plenty of room down the flanks in the early stages
There was a brief delay when the pitch sprinklers suddenly burst into life.
But West Ham started to look threatening and it needed a brilliant save from Foster to deny Cole the opening goal after 17 minutes.
Cole's close-range shot from Obinna's low centre looked destined for the corner of the net, but Foster somehow finger-tipped the ball onto the post at full stretch and it rebounded out.
Scott Dann blocked a shot on the turn from Piquionne and Roger Johnson did a similar job to deny Luis Boa Morte.
In a rare Birmingham attack Alexander Hleb picked out the run of Keith Fahey but he was crowded out as he prepared to shoot.
Scott Parker was forced to cut out one dangerous cross after good play by Hleb.
Cole should have done better after turning Dann inside the Birmingham box. But he failed to make proper contact on his shot and Foster was able to gather at the foot of a post.
West Ham needed only three minutes of the second half to break the deadlock through Piquionne's fourth goal of the campaign.
Boa Morte picked out the run of Piquionne in between Ridgewell and Johnson and he drilled his shot across Foster into the far corner of the net.
Blues tried to retaliate and Ferguson's angled ball almost picked out Larsson's well-timed surge into box. But the Sweden international failed to make contact and Robert Green was able to collect.
Cole came close to making it 2-0 when his glancing header was only just too high from Obinna's corner.
It came as no surprise when Behrami doubled the Hammers lead after 57 minutes. Cole had time to tee up the run into the box of Behrami and his first-time shot flew past Foster from 12 yards.
City manager McLeish responded by bringing on Jean Beausejour and Craig Garner in place of Hleb and Fahey.
The woodwork denied Boa Morte when his shot crashed against the woodwork.
Jerome gave Birmingham a life-line by reducing the arrears after 63 minutes.
Zigic headed a cross from Larsson into his path and the former England Under-21 striker made no mistake from close range.
After 73 minutes Ridgewell equalised and a question mark has to be placed against Green.
He only succeeded in pushing a free-kick from Larsson straight into the path of Ridgewell who made no mistake from eight yards out.
Birmingham came close to taking the lead when Jerome burst into the area and saw his shot deflect off West Ham defender Daniel Gabbidon onto his own crossbar.
Obinna was yellow carded after a late challenge on Larsson as West Ham held on for a point.