There are many benefits to human milk, "human proteins" is not why it is best.
"Our study describes transgenic cattle whose milk offers the similar nutritional benefits as human milk," Li wrote in the journal.
Breastfeeding: A mother's body provides immunities to mutually contracted virus. Milk supply is regulated naturally. (It's hard to underfeed/overfeed) Contents of milk change with needs.
The only way I see this being commercially available is if mothers are convinced it's a valid replacement. Most mothers are perfectly capable of breastfeeding.
Crazy-ass China.