The simple answer is NO. Once an app is Custom B2B, it's always Custom B2B.
BUT:
You can create a new app with a slightly different name and submit that app to the AppStore. For example:
Custom B2B App Name: com.yourcompany.AppName
New App in AppStore: com.yourcompany.App-Name
I'm not sure how different the names need to be but you can experiment until you find a name the AppStore will take.