I checked out that Air Canada 777-300. The explanation is quite simple. The VC model is included but Model.cfg will need editing to recognise it.
If you open the Model folder you should see two MDL files + a file named Model.cfg. The MDL files are named OS773ERV2--L.mdl & OS773ERV2--L_VC.mdl. (The latter is the VC model.)
Open Model.cfg in Notepad & you will see this.
[models]
normal=OS773ERV2--L
Change it to this to point it at the VC model.
[models]
normal=OS773ERV2--L_VC
Exit Notepad saving changes when prompted.
If you try the 777 in FSX you will now see something like this. The VC now displays but the textures are missing.

You can download the missing VC textures from the Posky site. Get the 32-bit set here.
http://www.projectopensky.com/downloads.php?aircraft=842ytv5p8&location=panelpackage(Note that these are the 777-200 textures which are exactly the same.)
Extract the file & paste the 26 texture files into the texture.aca folder of your 777-300.
If you try it in FSX now you should see this.

Hope that explains it. You can update it to the glass panel & gauges if you wish by downloading the appropriate files from the above link.