This is answered on WOT wiki's: http://wiki.wargaming.net/en/View_Range_%26_Camouflage_%28WoT%29

In short:

1. Several location are evaluated, at a different rate depending on the distance you are. Top of turret, Front, tracks are all evaluated.
2. No. The camouflage mechanism makes it assymetric. It may be true for the same tank, same crew level and camo paint/net applied.

-- Mr_Damage, playing now for 4 years.

This is answered on the WOT wiki.

In short:

1. Several location are evaluated, at a different rate depending on the distance you are. Top of turret, Front, tracks are all evaluated.
2. No. The camouflage mechanism makes it asymmetric. It may be true for the same tank, same crew level and camo paint/net applied.