I was about to create a new thread on formation tactics but saw this was here instead.
My personal usage of armour formation revolves around a 3 tank squad moving in the shape of a wedge. This is shown roughly below:

I have used this tactic multiple times to great effect, keeping enemy armour down and friendly armour losses to a minimum. This tactic is particulary effective on kashan with long range, easy to scan views and mimimal cover/obstacles.
The strength of the wedge formation is its rigid control of the tank placement by the squad leader coupled with the flexability to deal with armoured threats approaching from multiple directions. With a wedge, a tank attacking from the right or front right will encounter two tank barrels and quite possibly a strong armour facing stemming from the squads reaction. A tank attacking on the left faces the same problem. Best of all, a tank directly in front of the formation would face three tanks, with frontal armour facing, an extremely formidable threat.
Another advantage of the wedge formation is the re-arrangement of the formation if the lead tank (the most likely tank to get hit) takes damage. The lead tank can swap with a rear tank and can then take a step back from future enemy fire if quick repair support is available.
The distances the tanks should keep from each other should vary depending on cicumstances and the type of threats that could be encountered.
I recommend keeping a distance of 20m from lead to rear tanks and a distance of 50m between the rears when enemy jets are known to be out of action, this ensures that the formation is close and the tanks cover each other well with cover/terrain minimally blocking the view of all three gunners.
When enemy jets are up, the distance should be at least above 30m and preferably 50m from lead to rear and up to 100m from rear to rear. Trust me when I say laser guided bombs are hell.
I'd like to know any thoughts and opinions on this tactic, perhaps some constructive criticism even from one armour player to another.