Reproduced in 4.3.0b3
1 Open attached project
2 Open scene "1"
3 Press play - notice message in Console
4 Press Play to stop and select Btn1 in Hierarchy and turn on "Is Trigger" of Box Collider 2D
5 Press play - notice no message in Console

In the scene I have, Btn1 has a collsion2D body with 'trigger' turned on. Now this should call the trigger function of Btn2 which has a 2D rigid body, a 2d collision body and a script with the right functions.
Atleast, according to the table here: http://docs.unity3d.com/Documentation/Manual/Physics.html