I did the following, more or less for learning. There is a network printer in our LAN. I installed CUPS in a Debian Squeeze VM (no GUI), opened up the CUPS webinterface into the LAN, visited http://ip.addr.of.debian:631/ in a browser in a Win-XP and got the test page printed. I have now a printers.conf in the Debian box which goes like this:

<Printer hp_lj_on_deb>
Info HP LaserJet ....
MakeModel HP LaserJet 4250 Foomatic/Postscript
DeviceURI socket://172.18.1.254:9100
...
Shared Yes
...

Now I install CUPS in #! VM, visited http://localhost:631/ in it and created a printer which is connected to hp_lj_on_deb above. The printers.conf says:

<Printer cb_printer_to_deb>
AuthInfoRequired none
Info HP LaserJet 4250 through deb
Location office
MakeModel HP LaserJet 4050 Series Postscript (recommended)
DeviceURI http://172.18.1.241:631/printers/hp_lj_on_deb
...
Shared No
....

Now I open the printer installation tool system-config-printer to find out _two_ new printers there. The new one shows under properties "ipp://172.18.1.241:631/printers/hp_lj_on_deb" and has a different driver, "HP LaserJet 4250 Foomatic/Postscript on ...".

Who installed that? Does is bypass CUPS? cups/printers.conf has no record of it.