If the question is whether you should be able to take a PhoneGap project and convert it, then yes. However, they may need to tweak some things around plugins and config.xml depending on how old the project is. (Ex: There are some things in config.xml that are phonegap only)
Basically, copy the contents of what would go into the “www” folder into the root of the project.
On plugins:
a. If they are using base Cordova plugins, then they can just go
click the plugins in the manifest editor
b. If they used a PhoneGap CLI project, then for plugins they can actually copy the contents of their “plugins” folder to a “plugins” folder in the VS project
c. If they were referencing custom non-base plugins via feature elements (the old Cordova 2.x way), then they may need to make some adjustments – Mainly because plugins like push and barcode aren’t in plugins.cordova.io yet