Replacing 2 inch vertical cast iron pipe going through concrete
Since this unit is one in a building of condos, an improvised DIY job is not acceptable; the job must be done right. I would assume that there is a collar that the pipe passes through, that is, the concrete is not adhering to the cast iron pipe.  I would think that you must remove the broken section by making at least three cuts with an iron pipe cutter.  Then insert a new section and connect with approved couplings.

Find out if you can use PVC or ABS plastic for the replacement section. The  replacement section may have to be in two parts if the hole is tight. Really sounds like a professional job to me.