As I noted in the comments of the suggestions for NameMapping sharing, for NameMapping, this is implemented. However, it is not currently implemented for the TestedApps file. I believe it has to do with an embedded GUID in the TestedApps.tcTAS file that TestComplete recognizes that it already is present in the project suite. So, for now, TestedApps.tcTAS cannot be shared. There are other project items for which this is true.
HOWEVER... you can copy and paste the individual TestedApps items from one project to another. In Project 1, open the TestedApps item, right click on the app you want to make a copy of in project 2, select copy, go to Project 2, open the TestedApps item, right click in the panel and select "Paste. Not quite the same, but it is easier than having to recreate your TestedApps from the ground up.