What is the standard rule for running 12-1?
Here is my opinion.

1) I have never seen it played where 11, 12, 1, 2 was allowed.

The official printed rules say...


  RUNS: A run is made of four or more cards numbered in order. EXAMPLE: Part of Phase 2 requires a run of four, which could be “3,” “4,” “5,” “6.” The cards may be in any combination of colors.


2) The official iPad version of the game does NOT allow 11, 12, 1, 2. (I tried to make sure)

3) I found an updated version of the rules on line...


  Run: A run (similar to a straight) is made of four or more cards numbered in order. The cards do not have to be the same color. A run may not go in order of 11, 12, 1, 2; this is an illegal play. Runs must stop at 12 and only start at 1.


So, I would say that 11,12,1,2 is NOT allowed.