I am finding:
1) Create a PAGE, and VIEW MODEL
2) ON the Page:
Add a Tab Control with TWO Tab Items, on each Tab Item add a RadMap and a ComboBox
3) In the VM Create an Observable Collection of Providers and assign to both Combo Boxes on each Tab Item.
4) In the VM create a property(INotifyPropertyChanged) for each SELECTED Provider from each ComboBox, and BIND the Provider to each Map's Provider Dependency Property. (One List / Two Selected Items /Two Maps)
5) Run the App, switch between the Tabs and switch between the ComboBox's Selected Provider and you get botched providers displaying mixed data.
I have determined that when tabbing from one TabItem to an other, the RadMap gets Unloaded and then Reloaded each time, and several resources gets messed up because you do not call the DISPOSE. But, in fact you cant or else you would not be able to tab back... so there are several additional week references that are not detached and memory will continue to leak leading to poorly managed provider tiles etc... Either that, or there are static references that both Maps reference... That I am not sure yet, still investigating and leaning on the Provider itself.