Actually, I can't find any english articles on Wiki to explain the whole idea, but here's some useful links to understand the concept :

http://www.scmp.com/business/global-economy/article/2099244/chinas-bay-area-next-big-thing-where-it

http://www.scmp.com/topics/greater-bay-area

http://www.scmp.com/news/china/policies-politics/article/2135514/beijing-pushing-forward-greater-bay-area-plan-top

http://www.cmab.gov.hk/en/issues/bay_area.htm

Hey hackers , what do you think about greater bay area in China ? Will it really greater than "Bay Area" ? Interest Declared : Developer from Hong Kong