On 30th Oct when your COS to H1b was approved you can no longer legally work for your L1A employer.
If the start date on the LCA and the petition is before the approval date, then you must begin work immediately for the H-1B employer. You are not given any grace period. In fact, if it was approved October 30th and your supposed start date was October 1, 2013, you aren't penalized for not starting before October 30th, 2013 because you did not have an approval, but [b]you have gone out of status[/b] if you did not begin work as soon as the H-1B was approved. If that is the case, if that is what has happened, then the only way for you to be safe will actually benefit your L-1B employer. You can give your L-1B employer notice, maybe 1 or 2 weeks and as soon as that time passes, leave the U.S. and go to your home country for H-1B visa stamping. Then you come back and it erases any gap from before.
I found this out yesterday as I was in the same boat and my H1b got approved on the 26th while I was blissfully working for my L1 employer. If you applied through a consultancy the best way forward would be to:
a) Immidiately submit resignation from your L1 employer.
b) Ask the consultancy to start running your payroll from Oct 30th onwards.