ZTZ-99 "a2" isn't new, its 2008, ZTZ-99A is the new MBT they are using which is not deployed in Vostok
Ikalugin convinced (dragged) me into this forum to tackle the chinese questions but thanks nonetheless, Yes, i've seen the wiki claim but a lot of info out there in the internet about chinese stuff is wrong or falling wrong speculations....
as for Armor level, I'm can't say much about it other than it is a mix of Steel and Ceramic "Composite" kind of armor, I think it can withstand 23mm AP from the front from 1 click out and .50BMG from 100m in the side.... Ah don't quote me on this, this is from discussions i had and we didn't really touch upon it too much because its an APC....
This is fairly common in china as Production of new gear despite how large it is due to chinese industrial capacity is not fast enough to modernize the PLA at an effective rate due to the PLA's large size (Too large, they have too many tank divisions for one) I'm guessing the brigades sent to vostok was recently re-equipped last year with the ZBL 08s