Garth, agreed about being in the box. But batter standing on the line, is "in the box". And if his toe happens to touch up against the plate, or even on it a bit, then let the play happen. And then rule accordingly. If the batter then did something against the rules, call it. Can benefit the defense.
Found this, and could use a reference, and does make sense:
http://www.eteamz.com/baseball/rules...ory.cfm/batter
Scroll down to rule myth #5