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 ,
Nothing is impossible especially now that the most respected investment companies have an interest in Bitcoin. With that being said, the citizens of Nigeria appear to be enthusiasts of cryptocurrency but the stance of their government appears not to support BTC which shows that what you said can't happen for now in the country.
Central Africa Republic is the only African country with the possibility of using BTC to pay salaries.
I believe other African countries governments will never like the idea of paying their worker's salaries in BTC which will limit their fiat currency usage.