This would probably require some documentation from Valve. hope this doesnt leave me sounding like an idiot...but...i was killing some time today and i came across something that might peak your interest.
Chris' FPS Configs for TF2 - Different configuration files to automatically set all settings to their absolute lowest or highest.
It is recommended to troubleshoot before resorting to these as they can cause problems.
An FOV slider is available within the options which is limited to 75-90°. The actual FOV will be adjusted for other aspect ratios, meaning widescreens gain a higher than configured FOV except in windowed mode.
Console commands can change the FOV to values below & above the slider's range.
About: GCFScape is an explorer like utility that enables users to browse Half-Life packages and extract their contents.