You can connect multiple open-collector/drain devices together on the same line, but not multiple push-pull since they will try and drive eachother differently.
the first answer to your reply is almost right. you should
note that in push pull, tha output has voltage all the time , but in
open collector (or open drain in mosfets) the output stage only pulls
current (a good zero voltage) but when the base of transistor goes to
zero, the transistor gets off and the collector floats and has no voltage.
you can tight open collector outputs together in data buses.