I think this concept has no meaning. Citizenship applies to humans not corporations.

As there is no world government, citizenship is practiced by individuals on the national level. 

Do you think “global corporate citizenship” is a useful concept?

I think Global Corporate Citizenship is a very useful concept as it makes corporations more ethically responsible towards society and environment. Owing to its benefits to the business and society as it not only enhances a business’s reputation in the books of its stakeholders but also benefits the society at large, this concept is being increasingly incorporated into the strategic planning and management of businesses these days. This concept resides on the notion that it is the ethical responsibility of the businesses to give back to society in return of what they got from it (in the form of resources) to gain profits.