My company has just secured a contract for Montreal. I'm having a tough time getting information on the electrical requirements for Control Panels. Does anyone know if they require CUL or any additional CSA certification? Also, what is the nominal three phase voltage in the Quebec province. I'm hearing both 575 and 600VAC, are these interchangeable?

We will hire a local contractor for the installation but the control panel will be manufactured here in the US. If anyone has any information on the requirements it would be helpful.

MGD
You might wand a quick view of the post on extra low voltage wiring for a long explanation of approvals.

If the factory that supplies the control cabinet has a product approval agent Like UL they should be able to apply a Canadian Standard and apply an approval label Like cUL to the cabinet before it leaves the factory. Otherwise you will need to have an on site product approval done in Montreal. I am in BC so cannot help with Montreal conditions or inspection athorities. From the US UL and CSA should be able to help at the factory.
Nominal voltage is 600/347 and 575 is covered at 600. the other nominal Canadian voltages are 120/208 120/240. all those are from grounded systems. 277/480 is a nominal US voltage and there is lots of US made equipment in Canada supplied with 480 volts.
If the location of the work is supplied from an ungrounded system then the voltage will be 600 volts with no 347(voltage from phase to grounded circuit conductor) I mention this in case you have any control transformers with a 347 volt primary which won't work very well if the supply is ungrounded.