Sounds like bullshit.
Whatever they might be called in different countries, they all have one function. This is to prove that a foreign national is living and working in the host country legally. It's a "green card" for the US, and no doubt something exists in Canada if, for example, a US citizen moves there to live and work, but retains their US nationality and passport.
Since you were born in Canada, and have a Canadian passport, Moneybookers are showing (again) their incompetence. They may well want something, but they are not asking for the right document.
Their concern is probably that US residents are getting around the rules by registering as "Canadian" using a "borrowed" address. Since you have supplied a Canadian passport, this would not be the case.
Something has clearly got them suspicious in your case, as this is not normal procedure for having limits raised. Passport, proof of address, and bank account verification are normally used. This is very similar to Neteller, and I have been through this standard procedure there long ago.
Perhaps they suspect you are operating the account on behalf of another person, such as a US player, and it is being used to work around UIGEA. They need a watertight cover for their asses in case this proves to be true. They can do this by showing they took every possible step in verifying the account before upgrading it.
Surely Moneybookers know what they want in the case of a Canadian born and resident citizen who has already supplied the passport - but there again, we know how inept they are
Maybe they would accept a DNA sample instead