Is it permissible for an engineer in an oil company to inspect the summer recreational units designated for employees, knowing that these places are predominantly used for unlawful activities? And is his doing so considered a form of cooperation in sin, or does his inspection of the apartment as an apartment not fall under that category?

We do not see your going to inspect the places as an aid to disobedience, because the possibility of sin does not necessitate abstaining from the work. Selling grapes to someone who will turn them into wine is forbidden if the seller knows this; otherwise, it is disliked. It is disliked to sell grapes, dates, and weapons to someone who is feared to use them in disobedience. However, if this is not confirmed, selling is not forbidden, but if it is confirmed, then it is forbidden.