Assuming that the Irix install CD's are not in efs format - my eMac
certainly can't read Irix install CD's (just tried it now with Irix
6.5.13). Not sure if you could rlogin from an sgi and read the cd's
across the network, could be worth a try - after all, it's not the Mac
that needs to understand the data.
Couldn't you borrow an external scsi cd drive from somewhere? :-)