My superintendent doesn't even have my key. Once, when I was living here alone, I asked him to keep my key, just in case I lost mine or something. He said that he would, If I absolutely could not find someone else I trusted keep a spare key for me. He really only likes to keep keys of tenants who are elderly, at the specific request of their family members.

Even when they had people come to all of the apartments to install new toilets and shower heads, the super had to go from door to door, making appointments so that people could be there to let the workmen in.

I don't know, but it does sound strange to me that they would go in your apartment without your consent.