More than likely, until a ticket agent moves in, it will be a very large broom closet. Most enclosed & heated Metra stations located in the suburbs are maintained by the municipality they are in, who are going to find it easier to keep a broom, mop bucket, etc in the unused agent's office so they don't have to unload all that stuff out of their pickup truck everytime the station needs to be cleaned. There are some stations around which are indeed heated "indoor" stations but have no broom closet or anything, and I've always thought those must be a pain to clean.
That old car might be worth money!