I have recently been in Khovd (October 2101) and authorties there assured me that you can not cross the border into China at Bulgan. I asked multiple sources and received the same answer. It seems very unlikely that you will be able to cross by just showing up at this stage.
However I did receive information from a guy at a travel travel agent in Urumqi that he could arrange everything. His details are :
www.china-holiday.com/english
markinfo@163.com
He claims he can organise a two-day tour that will take you between Urumqi and Bulgan. The cost for is US$960/1380 for 1/2 people. I did not try this myself.
There are now AeroMongolian flights that fly from UB to Urumqi via Khovd. they cost $US173 oneway from Khovd so are a far better option. Ez Nis is also starting the same flights.