H1B approved w/o COS from L1; cannot start on oct 1 with new company

I am currently working for company A on L1(in US), and company B applied for my H1B and the petition got approved with start date of october 1 2013.

This petition was approved for consular process(abroad visa stanping) and not as COS.

Q1: Can a COS be filed by comapny B now ? How much time does it take for COS to get approved?

Q2: Since this is non COS H1B, i can continue on L1 until the COS is approved but assuming that COS is approved on November 10th, does this mean that i will have to immidiately stop job @ company A and same day join company B or will there be some time to provide notice to comapny A and join company B with some time buffer?

Thanks in advance.