Hi Amit
MDG hub in nothing but ECC server only with activations of MDG Releveant business functions.
This is the reason deployment options as hub(Standalone) mode or co deployment mode is possible for MDG.
If you want to use MDG hub also it is on ECC server and and you can send your MDG hum master data into Targety system which is may or may not be ECC system.
Hope this clarify your question.