I don't know if the government of any African country have adopted the system of paying salaries in Bitcoin, but I know here is Nigeria they haven't, it's possible to pay employees using Bitcoin or other crypto currencies ,
With the services of some crypto currency payroll agencies like Bitwage,papaya global, ontop, which will make it possible for the government to pay their workers in Bitcoin or other crypto currencies and can be sent into their digital wallet,
Since it has to do with the government another agency can be set up in the country in respect to paying salaries as Bitcoin which will somehow help in the growth of the economy of the country.
African countries will first adopt Bitcoin as a legal tender before they can start to talk of paying their workers salaries in Bitcoin, with the adoption it will be more convenient for them to pay salaries in their local fiat currencies. Central African republic, is the only known African country that has adopted Bitcoin as a legal tender and only them can easily make that kind of decision to pay workers with Bitcoin. I believe that private companies in Africa, can decide to pay their workers with Bitcoin, so far it is not banned in that country, but many workers will prefer to be paid with their local fiat currency, so that they can easily spend it in their country. With government adoption as a legal tender it will be easy to transact Bitcoin in any country.