Blood Bowl Handbook, page 21:
"The coach must declare that one of his players will try to intercept before the throwwer rolls to see if he is on target."
This one is so obvious, I can't understand how people found it unclear

6. Should Hail Mary be affected by TZs - no. If there is no dice roll needed to complete the action, there can't be modifiers. How do modify a non-existent dice roll? (BBRC would have to add a base AG roll needed to complete the action. I dunno if that's needed or not. Hail Mary is a team's ONE way of "punting". Without that, there'd be no reason at all to take it as a skill.
"No dice roll needed"? From the Death Zone Playbook, page 11:
"On a roll of 1 the player fumbles the throw, and the ball will scatter once from the thrower's square. On a roll of 2-6 the player may make the pass."
Read the rules, kids - sometimes they're good for more than discovering inconsistencies

Cheers!
-Chet