Well are these A and B leads associated to the same Account? If so, you may be able to say
if A Lead 1 Has Opp=XYZ
then populate a Static List of leads from this Account with Type B
then send an email to this static list.
Without a better understanding of your existing data structure, this is tough question. You should discuss this with your CRM Admin in more detail. I don't really get what you mean by B leads can View/Transact on Opps from A Leads. Are you running some sort of Partner System?