A bit of a late followup, but Yani on the CorelDraw forum shared a neat trick. I didn't even think to try, but it turns out you can get somewhere by:
1.) using the 64-bit postscript driver from another fiery rip printer in conjunction with
2.) the ppd for the canon in question which you can get from the package supplied for mac driver
In my case, I actually installed the 64-bit driver for a xerox Fiery EXP250 PS and the ppd for the irc3220.
I haven't been able to get a 100% match to the color output from the 32-bit canon driver for the imagepass c2 (color output options are slightly different), but for non critical work, it's close and so far I haven't seen any output glitches as I was expecting.
At least it works and in some ways the output is noticeably better to my eye than the 64-bit canon-supplied pcl5e driver (since there is no 64-bit canon-supplied ps driver for these older rips.)
Next I'll try the older irc3200 and imagepass c1 and see if the same works.