@boonebgorges wrote the following recently http://wordpress.stackexchange.com/a/45682/7401 which seems relevant to your question…..
The article only mentions Networks + to enable multiple networks which is a premium plugin.
There is also a free plugin, by @johnjamesjacoby, to enable multiple networks https://wordpress.org/extend/plugins/wp-multi-network/ but that apparently is no longer compatible.
It has been patched ( http://alantait.net/2011/07/27/wp-multi-network-plugin-fix-for-wordpress/ ) and @johnjamesjacoby mentioned in the comments of that page ( 12/02/2012 ) that he planned to update it soon…
