Is there any PRACTICAL difference between a "Network Engineer" and an "IP Engineer" ?
The practical difference is whatever your company defines the two roles as, pretty much. Practically speaking.
For example, a system administrator has a generally accepted definition, but if you ask sysadmins what their job responsibilities are it tends to get rather nebulous at times...one may have to answer support calls from users and another never sees users. Instead it comes down to the organization and size of organization.