ANSWER:

The reward is not the same as a masjid as this hall can be changed by the owners into anything if they want. However, it is permissible to pray there in Sha Allah. 

My extended family has been living in a apartment building. The building has a prayer room with an assigned imam employed by the building management.The prayer room is taken care of by the building management and All 5 prayers are done there in jama’ah. My question is is praying in the above prayer room same as praying in a masjid ? They’ve been there for decades assuming its same as masjid