Australians spending two nights in Guangzhou of week in HK - do we qualify for visa-free transit?

We hold Australian passports and will spend a week in Hong Kong. We do that without needing visas each year. But this year we will catch new train from Kowloon to Guangzhou (Canton) for stay of under 48 hours in mainland China. Do we qualify for free transit, or do we need tourist Ls for China?