The little houses over the stairs were torn down sometime in the 1970s. The spots where they used to be are now steel plates in the sidewalk with yellow signs that read, "DO NOT BLOCK--EMERGENCY EXIT". I'm not quite sure how to get to those exits from INSIDE the tunnel though.
What's more interesting is why there was a Eureka Street Station at all. Yes, it did allow those living west of Castro to enter the tunnel without having to walk the 2 blocks or so back to Castro, but that seems to be rather extravagent.
Back in the 1970s, Father John McGloin, S.J., of USF's History Department (and creator of SF History I & II), found some evidence in old city records that suggested that Eureka Street was originally planned as a transfer station for a "Richmond-Mission" streetcar line that never came to be. Interesting when you think about it--two densely populated areas of SF that even today, are difficult to reach from either place.