Any Physicists or Electricians here?

[Krayce]

In the case of a 3 phase line, A, B and C lines carries a voltage, each one of said lines has a reference level (ground), and when you touch one of those lines (any of the 3) and you are touching ground you get electrocuted, fried, you hang in the sneakers, in other words you are dead.

You can even be electrocuted without touching anything if you are near to a high tension place (eg. air connection...).
We can illustrate what you said by this image below, instead of letters A/B/C I used numbers 1/2/3 (dedicated to Assault Cube FTW):

PS: Sorry for the image quality, I have again a prehistorical phone with 2.3MP!

In case you wonder why birds are not fried when they are standing in a live line is because the voltage difference is zero, therefore no current flows across the birds.
Hope that helps a little bit.

Yep, and because they touch only 1 live line, if they touch 2=dead.

Remember Ohm's law: V=iZ, or in this case, the one you're interested in can be rewritten as i=V/Z.

Yeah, and you can simplify this by;
i=V/R"omega"(live line)+R"p"(protection line)

When you say "shocked", you mean that you can feel the current running through your body. I believe you can start feeling it in the 3mA range, but I'd have to look that up again.

In fact, this start at 0.5mA in AC and 2mA in DC

Human body resistance is:
5000 ohm (no wet)
2500 ohm (wet)
1000 ohm (immersed)

Tension contact:
25V (wet)/ 50V (no wet)