It is confusing to me as to which fares I can directly access from the aircanada web site, which fares I can access by calling the Air Canada telephone reservations agent, and which fares do travel agents have access to, via their computers.

The air canada web site states that econo and latitude fares are "web exclusive". Tango, econo, freedom, fund, and executive are amenable to booking, both by the web, and through the reservations agent.

I wonder if all of the old booking codes - eg V, H etc, can still be booked through the telephone agent, or not.

In terms of a travel agent, assuming that he/she does not go to the air canada web site, but uses his/her own computer - it looks like they have access to all fares, including econo? and latitude fares. I can confidently state that, because a travel agent has booked a transborder fare for me, and the booking code is "A" - one of the latitude fares.