I have solved the problem of remote stream injection - there's an option in #IceCast called <fallback> stream which is a secondary stream to which the listener is 'moved' when primary stream drops. <fallback-override> then allows to move the listener back to primary stream when it appears again. To listener it appears as a single audio stream. This is perfect for my case tomorrow where I will be streaming from the club to my OBS in the studio when I won't be there.