There seemed to be two types of code. LZxxxxUS are the actual tracking. LCxxxxUS is not tracking but a custom code. You can only find status of LCxxx after the parcel land in the receiving country, as what Ivan said.
oddly enough, the last 2 characters of the customs code (which can sometimes be used for tracking) are supposed to be for the country it's being mailed from. US is the code for USA. Why is that on a canadian customs label? I guess the person got a stack from a usps location in the USA and brought them back with them to mail with ?
I haven't received anything recently from canada, so it's possible they use the US country designation for customs codes, but i can't imagine why.
Anyway, it's common for things to not be trackable until they reach their destination country anyway, so try to plug that sucker into the SG post website in a week or so.