If there is a system to keep track of the mother who donated (in fact sold) the milk, then why not. At least a Muslim baby should know when he grows up who are his or her siblings according to Qur'an.
But they are planning to mix the milk and not tracking the mothers, then better denounce Islam as the state religion.
This is just one issue. In a country like Bangladesh, it will bring more harm. Poor mothers will deprive their own babies to earn money. It's a good idea and it can be implemented in future when Bangladesh's per capita income will be crossing USD 25000 in Shaa Allah, society will be digitized and the electronic record keeping will be widespread, and poverty will decrease to less than 1%. Even then they will have to keep it as a "donation" rather than a commodity for sale to keep the people from abusing this.
Or there is always a second option, just take out the particular verse from Qur'an that's taught there, or declare Bangladesh a non Muslim country.
The person who you are debating with belongs to a culture where they can marry step sisters.