Altium readspads, pcad, allegro,orcad,, zuken and a few otherswithout problems
Profesionally i need to interact with customers using allegro , boardstation, pads , orcad and zuken.
They send me their databeses and i simply load those in altium done
The way back is another story though... It is up to the other tool vendor to read altium. But you can always go the gerber orodb++ route