Arnold has plausible deniability here. Go to http://gov.ca.gov/press-release/13575/ and scroll down to AB1176. Then click on the See attached veto message link and you'll indeed find the veto message with the letters lined up as posted above.
But if you instead click on the AB1176 link, and then scroll down to the bottom of that page and click on the Veto Message, you'll see the same wording with different formatting which obscures the hidden meaning.
So yeah, either Arnold or one of his staff members played with the formatting to make it come out just so. But they can claim that it was purely coincidental, and point to the other version as evidence to that effect.
I'll be curious to see how long it stays up when word gets out. I took a screen shot just in case, and I suggest others do likewise.
Does anyone really think Arnold types his own letters???
The AB1176 link you posted has been reformatted by the legislature. Take a close look at that URL to see the source. The pdf from gov.ca.gov is the real thing from the governor’s office.