Again? There were some sort of bans in 2007 and 2011, but I don't thick anyone ever noticed. It's a bit like "free education": every post-independence president has declared primary education free yet primary-school kids still have to pay all sorts of fees or go home.
Anyways ... before worrying about plastic bags, the country should first focus on cleanliness in its towns and cities, which are where these bags get used the most. Walk around any such place in Kenya, and you will find huge mounds of festering filth, raw sewage being dumped all over the place, etc. A transfer of garbage from plastic to paper won't make much of a difference.
Also, my guess is that recycling plastic is not such such a huge issue in Kenya, given that many people already "recycle" through use.