Absolutely, Mobile Services is very much designed with this in mind.
You can
- call Mobile Services from other services (in Azure, or anywhere else) thanks to the HTTP REST API: http://msdn.microsoft.com/en-us/library/windowsazure/jj710108.aspx
- call other services from Mobile Services using server scripts and the request module: http://www.thejoyofcode.com/Making_HTTP_requests_from_Scripts_in_Mobile_Services.aspx
- connect DIRECTLY to your Mobile Services SQL database from anywhere. This is just a SQL Azure database so you can use the connection string to connect from another service in Azure (or even beyond)
- add additional functionality to your SQL database (like stored procedures). It's just a SQL database!
- invoke T-SQL from Mobile Services scripts using the mssql global module.
Lots and lots of composition options, so the short answer is YES, definitely!