Not definate recommendations, but would suggest asking, or give them a call, at the university here, Dufour or Mail,
(They are always very pleasant and helpful at the reception).
I thnk they will be your best bet here..
They could maybe point you in a couple of directions, depending what you were wanting exactly
Not sure about Geneva, but despite the digital advances, apparently in many current photography degree courses, the students still have some studies based on the dark room.
Maybe a long shot, too, but the Maison de quartier de St Jean has a dark room and you can hire slots to use it.
Maybe they may know of someone too, or one of the photographers that use it, might do...(???)
Maison de quartier de St Jean,
8 chemin francois-Furez,
CH-1203 Geneve.
Tel 022 418 91 50.
Bus 7, arret Contrat-Social
Good luck. Hope you are successful in finding something!