A friend on a NZ passport flies through Vancouver tomorrow, and has a few hours at the airport between international flights. Can he exit to the 'outside world', given he has a valid passport etc? His luggage would be checked through to London anyway.
(An authoritative link would be appreciated, if possible)
If you're friend wasn't from a Visa Waiver country, then they'd need to get a Transit Visa anyway, whether they were just changing planes or entering the country formally. The list of countries needing that is here. Getting a Transit Visa is free, but you do need to apply in advance.
For your friend, he'll be arriving as a visa exempt visitor, so will need to enter Canada anyway. At that point, he's in the country, so is fine to leave the airport. However, if he only has a few hours, he may struggle to get very far once he has passed through immigration, and factored in the queue to clear security again!
Canada is like the US, and requires you enter and leave (for the purposes of immigration) when changing between international flights. (Some people on their way through Canada to America who have US visas now don't need a Canadian transit visa too, but this is fairly recent and only covers some countries).
(It's not like somewhere such as Singapore, which doesn't require visas for international transit, and even has hotels on the airside so you don't need to clean immigration just to have a kip! Singapore also sometimes does short visit visas for people with a long layover, often including a free city tour, but it's a very different setup to Canada)
YVR has a special handling system for people arriving internationally and transferring to a departing international flight. While your friend will technically be on Canadian soil and have to clear Canadian customs, the process is streamlined and such passengers are essentially cordoned off.
YVR's website has a set of questions that can be answered to clarify matters.
Having flown through YVR on numerous occasions, a "few hours" isn't really enough time to get in and out. Getting out of the airport won't really get you anything, as to get to downtown Vancouver from YVR is a 30-minute SkyTrain ride each way. The "past security" side of YVR has many amenities like restaurants and shops, so it's not a complete bore-fest sitting at the gate.
