I do not believe that the Premiere Elements Mac project file (no matter what version of Premiere Elements) will import into Adobe Premiere Pro CC 2015 Mac ...by the way, what version of Premiere Elements Mac are you using?
For the definitive word, you would be better served asking this question in the Premiere Pro Forum.
From the Adobe Premiere Pro Import Formats Supported list, it appears that, if it works there, it is a Windows Only perk for prel files from Premiere Elements.
Have him send you a small project file and try it.
From what you have written in these forum threads, you are a Premiere Pro user - Windows or Mac?
Have you been able to import a Premiere Elements Mac project file into Premiere Pro CC 2015 Mac project?
Have you been able to import a Premiere Elements Windows project project into Premiere Pro CC 2015 Windows project?
As of now we do not know what version of Premiere Elements Mac is involved here. So, any example that you have of can do will suffice.
I use Windows 7 and Premiere Pro CS5.5 and have used Premiere Pro CS4 and Premiere Elements 3.0.2.
I have been able to open Premiere Elements 3.0.2 projects in both Premiere Pro CS4 and CS5. Some transitions and effects, of course, did not work as they were not present in all versions.