Advance is a community of Australian professionals overseas headquartered in New York City, with established chapters in Boston, Chicago, Los Angeles, San Francisco, Washington DC and London with several others in formation around the globe. Advance recognises the importance of maintaining connection with the one million Australians in our diaspora making their mark in boardrooms, science laboratories, arts institutions, classrooms and communities worldwide.
Advance is working hard to encourage brain circulation, but they soft sell the return with an understanding that many expatriates prefer to remain abroad. In that case, the primary focus is on enhancing connections with Australia. Advance recognizes that the diaspora has value regardless of its location.
I think Advance offers the best model of diaspora networking I've encountered. I could see something similar working well for Pittsburgh.