Your examples are all grammatically sound gerund clauses. They may be employed in a variety of ways:
As a Subject NP: John's having been late caused us many problems.
As an Object NP: The owners enjoy there being people at the hotel.
As a 'supplemental' Absolute Clause: There having been people at the hotel, the owners suffered no loss.
As the object of a preposition: The taxi drivers were greatly annoyed at people having had cars.
Your last example can also be interpreted as a noun plus a modifying participle phrase:
People having had cars were invited to post photographs of them.