One model could be the New York Port Authority, which crosses borders from New York City into the adjacent state of New Jersey. Even so, such grand visions and glib talk about regional synergies come up against some hard realities. Though under China's flag, Hong Kong and Macau are separate customs territories. Every resident of the SARs who travels to Guangdong must pass by a customs officer. Both SARs, for example, have their own currencies, even if Hong Kong dollars are as welcome in Shenzhen as Chinese renminbi notes.
History stands in the way also.
For the better part of 150 years, Hong Kong developed politically and even economically in isolation from China. The British went to enormous expense and trouble to build an artificial island for a new airport inside Hong Kong borders, rather than take advantage of the abundant, flat land just across the frontier, linked to the territory by an express train. Tung Chee-hwa, Hong Kong's first Chinese leader, paid closer attention to developing ties with Guangdong. Two days before the territory's mid-1997 return to China, Tung called on Governor Lu in Guangzhou. Yet official intercourse remains sparse.