It depends on the company, and of course on the domain name. I have some parked domains and they include the for sale link, but even with that I'm not really interested in selling some of them, at least not for less than a great offer.
If you ask the price most domain owners will reply with a high price or a "make an offer". Of course there are exceptions, some domainers don't want to loose much time. And others don't sell for less than a great amount because they really don't need to sell domains...
If you want to sticky mail me I can give an opinion based on the owner.
If it's a generic phrase, you may check DNJournal.com, NameBio.com or DNSalePrice.com to find comparable selling prices to determine a range. When submitting your initial offer, be sure to allow a significant amount of room for negotiation - don't submit your max price from the start. Also, I'd be careful to make sure the seller doesn't know you own the .ca or the price may go up.
Offer what you would pay for it. If you really want it, why beat around the bush?
If you are not in the ball park, at least you came in with your best offer and you won't have any reservations.
Unfortunately you sometimes have to beat around the bush or at least leave a little extra room to negotiate as some domainers simply take the initial offer and counter back at double that price.
In my experience, I've found it challenging to get the best price by offering my max price as the initial bid. Sometimes the "here's what I'll pay - take it or leave it" can work if you have a motivated seller though.