L1 to H1 with Receipt Number

[itstulasi]

Hi,
I came to US on L1B with Company A and my L1B VISA has expired on May 31 2011.

As my I-94 is valid till 2012 December, Company A has not applied L1 Extension and issued I-129S for me.

Now, Company B has filed my H1B Visa, I am waiting for H1 receipt number. Can I start working [from oct 3 rd onwards] with company B after getting receipt number of new H1 petition.

Thanks in advance,

Regards,
Tulasi.