Yes, it all depends on the letters. Better letters, higher prices. Haven't seen anyone specifically wanting to buy LLL.ca in the forums though.
I've been buying some L-L.ca lately. You can still get premium letters, and there are only 26x26 of them total. L-L.com have been rising in price and getting more in demand. You can't get premium LLL.ca at reg fee anymore, so L-L is the way to go IMO. They make potential good domains for companies with two words in their name, for example I think M-A.ca is an active site.