Help needed -- Considerations to be taken while migrating 2 different SCCM 2007 hierarchies into a single SCCM 2012 Hierarchy.

Question

Hi, I need your help on consolidating two different SCCM 2007 infrastructures into a single SCCM 2012.
We have two different SCCM 2007 Hierarchies, Lets say 123 and ABC
About 123 SCCM 2007 -- On 123 Hierarchy, we have already started migrating clients from SCCM 2007 to SCCM 2012.
About ABC SCCM 2007 -- On ABC Hierarchy, This is still running on SCCM 2007 (This hierarchy only be started migrating once                                      we
are completed migration on 123)
Out of which, we have few co located offices across the globe for both 123 and ABC. Now we are decided to replace the hardware on all these locations by removing the existing two servers (one for 123 and other for ABC,with two different Forest and domains),
and consolidate them into a single server.how can we plan/design to ensure that we covering both hierarchies SCCM clients for the operations.
===================Below are some possibilities we are discussing on================================
1.Is there any way on "System management" in AD to enable access either in 123's domain or ABC's domain.
2.Since we are planning to replace the hardware with Server 2012 R2 with Hyper-V, Create two instances and migrate 123 hierarchy to SCCM 2012 and other instance will serve ABC until we start the migration on this.
========================================================================================
correct me, If i am in wrong direction. Please suggest me the best of doing it. Thanks in advance.
srkr

Answer 1

1) In CM 2012 you can publish data to System Management in other forest but you have to configure the permissions manually and create the forest object in the ConfigMgr console.
2) CM07 and CM2012 instances can co-exist as long as you don't create boundary groups in CM12 for site assignment (that will cause overlapping boundaries if you still have boundaries in Cm07)
Kent Agerlund | My blogs: blog.coretech.dk and
SCUG.DK | Twitter: @Agerlund | Linkedin:
Kent Agerlund