Windows services create events in the global namespace as @David Lowndes pointed out. However, in order for a process running in a standard user's interactive session to open a named event created by a service in the global namespace using the "Global\" prefix the event must have a security descriptor that grants access to the user account or one of the groups to which the user account belongs.
Example code at Modifying the ACLs of an Object in C++ shows how to accomplish this by modifying the security descriptor for an object after it is created. Of course you would need to provide the specifics for an event object when adapting the example code.