Question about mutual transit and complex BGP peering

["Sriram, Kotikalapudi \(Fed\) via NANOG" <nanog () nanog org>]

Requesting responses to the following questions. Would be helpful in some IETF work in progress.
 
Q1: Consider an AS peering relationship that is complex (or hybrid) meaning, for example, provider-to-customer (P2C) 
for one set of prefixes and lateral peers (i.e., transit-free peer-to-peer (P2P)) for another set of prefixes.  Are 
these diverse relationships usually segregated, i.e., P2C on one BGP session and P2P on another?  How often they might 
co-exist within one single BGP session?

Q2: Consider an AS peering relationship that is mutual transit (i.e., P2C relationship in each direction for all 
prefixes).  Is this supported within one single BGP session?  How often the ASes might setup two separate BGP sessions 
between them -- one for P2C in one direction (AS A to AS B) and the other for P2C in the opposite direction (AS B to AS 
A)?

Thank you.

Sriram
Kotikalapudi Sriram, US NIST