I did some searching around, and taliensis belongs in the camellia group thea, which includes those that are used for tea production, although one of them, irrawadensis, does not produce caffeine. It is considered a wild tea plant that, at least in 2002, was threatened by habitat destruction.
Drinking a mengsa tea whose leaves look very similar to those pictured above, dark purpley green with thin yellow stalks, I believed that Yunnan Sourcing's new product had indirectly lead to my finding what all these strange looking pu'er cakes had been using as material: not our usual friend Camellia sinensis var. assamica, but a different species altogether, Camellia taliensis.
However, reading further along in the summary of the article by Long, Li, Ouyang, et al., I found this table of Yunannese wild tea plants, all of whose leaves are supposedly suitable for tea making:
var. crassicolumna China: SE Yunnan 1300–2300, evergreen broadleaf forest
var. multiplex China: SE Yunnan 1900–2210, evergreen broadleaf forest
var. shangbaensis China: S Yunnan 2450, evergreen broadleaf forest
C. grandibracteata China: W Yunnan 1750–1850, evergreen broadleaf forest
var. gymnogyma China: SE Yunnan, SW Guangxi, S Guizhou 1000–1600, broadleaf forest or scrub
var. remotiserrata China: NE Yunnan, N Guizhou, S Sichuan 920–1350, china fir forest or broadleaf forest
var. kwangnanensis China: SE Yunnan 1550–1850, broadleaf forest
var. kwangsiensis China: SE Yunnan, W Guangxi 1500–1900, broadleaf forest
C. purpurea China: SE Yunnan 1500–2200, evergreen broadleaf forest
var. assamica China: Yunnan, Guizhou, Gaungxi, Hainan; Vietnam; 100–1500, evergreen broadleaf forest
var. dehungensis China: S Yunnan, SW Yunnan 1000–1600, under forest or scrub
var. pubilimba China: SE Yunnan, Guangxi, W Guangdong, Hainan 240–1450, broadleaf forest
var. sinensis China: S China, SE Tibet; S Japan; N Myanmar 130–200, sparse forest or scrub
C. tachangensis China: E Yunnan, SW Guizhou, W Guangxi 1500–2250, evergreen broadleaf forest
C. taliensis China: W Yunnan 1300–2700, sparse forest / scrubThink of this next time you look at a "wild tree" pu'er tea that looks uncanny; it could be one of 16 different wild tea camellias!