Peering has everything to do with the physical interconnect and nothing to do with the ID numbers used to describe that interconnect, IMO.
On ISP level, routing tables are built via BGP. BGP needs Autonomous Systems (AS) as organization unit to work. If you are not an AS you are never a peer as you are not on equal footing.
As a rule of thumb, if your edge router has a default route set, we are very likely talking about different scales.