Just wanted to add my 2 cents worth.
Canon Japan seems to have created drivers for these printers - and are actually keeping them up to date. It is usefult to note that these printers were apparently released in Japan as the PIXUS 550i/850i/950i
If you install libpng.so.2 (seems to be an only libpng version) - I used the Redhat 8 rpm (I have mandrake 10.0)
Then d/l / install the PIXUS drivers (labelled as 550irpm PIXUS 550i [or 850 or 950])
Then d/l and install the CUPS rpm.
And hey presto - it worked on my system
I have done this sucessfully on Mandrake 9.1, 9.2 and 10.0, using the Redhat libpng.so.2 RPM from rpmfind.net
The latest version of the drivers seem to be a bit slim on the configuration options - but it does work.
Maybe someone smart can use these to build decent ones ???
Anyway - I hope this helps someone.