Exchange 2007 to Exchange 2010 Calendar Sharing

I am
currently looking to setup Calendar Sharing between two organisations.<o:p></o:p>

Company A<o:p></o:p>

Exchange
2007 environment with a mix of Outlook clients (Outlook 2010, Outlook 2007 and
Outlook 2003)<o:p></o:p>

Company B<o:p></o:p>

Exchange
2010 environment with outlook 2010 deployed to all clients.<o:p></o:p>

Requirements:<o:p></o:p>

Company A
and B want to view each other’s calendars and see the free/busy information.

I understand that an Exchange 2010 CAS server will need to be deployed into
Company A to allow the federated trust, which will allow for an organisational
relationship to be configured. To enable a subset of users to share their
Calendars/Free/busy info a security group will be required and the appropriate
users adding to this group.

The same will need to be setup at Company B (however without the need to add an
additional CAS server).<o:p></o:p>

my
questions are;<o:p></o:p>

1. will
this allow users in both companies to open calendars of users in the opposite
company (that are members of the security group)?<o:p></o:p>

2. Will
this also allow the users within the security group to be looked up via the
GAL?<o:p></o:p>