Hi,
yes, you can.
In the SEPM you can create a new domain to have a separated management of a set of clients even on a different AD domain. The only requirement is that your clients should be able to access to the SEPM in the other network, clients-SEPM communication is based on HTTP thru a web site installed in IIS.
You can test HTTP connectivity in this way:
in a client you want to check if it is able to contact the SEPM, open the browser
enter http://<SEPM hostname>:<port 80 or 8014>/secars/secars.dll?hello,secars
If you get "OK.", you should not have communication issues otherwise troubleshoot it as a standard HTTP connection to a web site in IIS.