A rare protest took place  in downtown Beijing on December 9, 2012 against the construction of the Shenyang-Beijing Express Rail line which cuts across the downtown area of Chaoyang district. Although freedom of assembly is protected by the Chinese constitution, in most circumstances authorities suppress citizen-initiated demonstrations. This time, however, the protest seems to have been approved by Beijing's authorities and the story was even widely reported in major media outlets. Sina Weibo, a government endorsed social media platform for public deliberation, even initiated a “topical discussion forum”  on the issue. Some netizens wonder if this is a sign of political reform following the 18th CCP Congress  new leadership.
Around 300 protesters demonstrated in Chaoyang district demanding the route of the Shenyang-Beijing line be changed. The protest was in reaction to a report by the Ministry of Environmental Protection  [zh] which claims that 37.27% Beijing residents supported, while 24.01% opposed the planned express train route which cuts across a number of highly dense residential districts in Beijing's downtown area. Many residents claimed that they had not done  any survey and were outraged by the result.
Below is a copy of the video at Tecent QQ video platform [zh] showing the orderly protest scene, which was quite organized with common slogans such as, “Against fake environmental assessment”, “Forced to agree”, and “Against the Express Rail passing by people's front door”.
Major domestic media outlets picked up the news quickly as described by Weibo user Sohu74  [zh]:
Within one night, the rational defense of the rights of residents along the Shenyang-Beijing railway line has become the focus of major domestic media outlets. The change is so sudden as if you have won a lottery. It is really hard to imagine and give response. Yesterday I overheard some conversation among police officers. A police officer asked “How come those with glasses [meaning those with good education background] also joined the demonstration?” Another police officer told the protesters: “please keep order, don't block the road or it will be illegal.”
Manipulating surveys is quite common in mainland China. What most people found surprising is that Chaoyang residents were allowed to protest in downtown Beijing. Reymon a finance analyst exclaimed  [zh] on his micro-blog:
In Beijing, the capital of China, a public assembly against Express Train project was approved. This is something really significant!
His brief comment has attracted more than 2000 comments [zh], some echoed, some doubted:
心安得理：If this is real, the party-state maybe able to transform. This is good.
亚洲陶瓷商城：十八大其中一个主要的议题 就是 “自由”吧？
亚洲陶瓷商城：A major topic in the 18th National Communist Party Congress is “freedom”, right?
帝都日记：December 10th. Sunny. First time for the empire. Story from the street: the police has approved the anti-express railway protest. According to the empire tradition, there are two kinds of assemblies, one is publicly organized by the government, one is privately organized by the government. Spontaneous organization is banned regardless of its nature. That's why there are so many mass incidents. Public intellectuals say, if citizen's assembly is becoming a norm, the government's authority will be restrained and this is a step towards democracy. It will have big impact to the future development of the country.
渴学家：too many good things happen will result in bounce back.
未曾顿悟已经年：hope such progress will not vanish quickly.
老虎啸山林：We applied for demonstration against forced demolition five years ago, nothing has been approved yet.
livelife在唱歌：The sun rises from the West.
亮中华之剑：This is a gesture made by the central government on the constitution. It seems that the government is ready to reform and protect constitutional rights.