H1 and L1 Conflict

I am working for a company A in my home country. I applied for a H1 visa through Company B and got my H1 Approved this year through lottery and all that process. Now Company B told me that we will do your stamping only after Jan 2015 and I have to join in 3 months after the stamping.
Meanwhile good or bad luck, Company A wants me to travel on L1B for 8 Months as soon as possible. Now I spoke to Company B and they are fine to hold on to my H1 stamping for another year.

  1. Now my question is when go for L1 from Company A to USCIS, will there be any issue or conflict? will my L1 get rejected?

  2. Also if it does will Company A know about the reason for rejection?

  3. And also company B tells me that if i am in US and whenever i want to switch over to Company B then I dont have to go for a stamping/interview. Just COS is enough is that true?

Note: I dont have any information about the LCA that was filed by Company B, so I dont know the date of commencement of job was given in that.