My team and I are in the middle of two active Exchange 2010 to Exchange 2013 migrations for separate customers. Both sets have exchange 2013 installed but no configuration beyond that. What we noticed in both situations is the the Exchange 2013 server can see the Exchange 2010 server but not the other way around. Example of what I mean. In the Exchange 2013 power shell you can issue the get-exchange server cmdlet and it will reply back with both the Exchange servers. If you issue the same cmdlet on the Exchange 2010 power shell you only get a result back of the Exchange 2010. So my question is this normal or do we have an issue. I'm proceeding with caution, so i have not moved anything yet.
On a side note, we also have another customer running Exchange 2007 server with Exchange 2013 install in their environment, this customers migration is in a holding pattern for contract reasons, but I did the same test on their Exchange 2007 power shell and it DOES give a result back of BOTH servers.