The important issues here are:(a) That TIG will not be selling...

The important issues here are:
(a) That TIG will not be selling any coal until June
(b) That since its coal is ex Russia, it is not impacted by the Dalian ban*
(c) That if China is positioning itself for diversification of supply chains post the Trump Tariffs, then TIG should win purely because of the size of its resource.

Australia has an FTA with China  so the fine print of that would need examination:
-has Australia already breached the FTA by precluding Huawei from our 5G network?
( keep in mind that Aussie 5G has not happened yet so there is no concrete evidence of Chinese bugs in the system)
-does this Chinese ban on Aussie coal to Dalian ports breach the FTA? ( effects 5% of China's coal imports)*

To speculate further on China's motives for this sudden change beyond those given (environmental & quality) is more suited to the Political threads, IMO, and is not likely to contribute productively to the discussion of TIG and its prospects.

TIG needs mega bucks capex to build the 12 month/year port & the connecting railway so, IMO, it would be opportune for management to investigate a Chinese JV for Aamam so that its development to 10 mil T/P/A can be advanced by 2 or 3 years.

Just imagine 10 Mil t/p/a at say $100/ton AUD NPAT ( $1 billion NPAT) ,  55c eps or $5.50 P @ a P/E of 10 Even half this on a Chinese JV would be awesome! The Chinese have the capacity to build the port & railway within a few years and our Board & Management should be taking advantage of the China/US debacle now rather than later, IMO.

In summary, this is a stark reminder that we should always consider where our economic interests are before we pay lip service to international politics and/or political/economic ideologies. China has kept us out of recession from 2009 to 2012 through its economic stimuli which seen unprecedented investment and demand for our resources. At present our trade surplus with China is $40 billion+ while our trade deficit with the USA 
is about $18 billion. If China applies Trump medicine to us, we'll have massive trade deficits & our Pacific Peso will be worth the proverbial two bob!

* It may not be coincidental that this is happening at a time when China's cost of iron ore imports has hiked by nearly 15% due to the Vale dam disaster in Brazil which has taken almost 5% of seaborne iron ore off the market. (I'm now speculating here: perhaps this is a Chinese strategy to balance trade and, in particular, the input costs of its steel manufacturing?)