Why not? Harrison is crap but hes a legitimate heavyweight, this isnt a mandatory and Harrison is also a current heavyweight European champion. Its a crap fight considering who Haye could of fought but how could the WBA not sanction this?
I think WBA moved Harrison into the top 15 and he can fight any ranked contender that he wants for a voluntary defense. Even if Harrison is completely undeserving of the ranking and this fight is ****.
Haye already fought his mandatory challenger. So this a voluntary (and crappy) defense. The WBA does not have to sanction it. But If the WBA don't sanction this fight, then they don't get sanctioning fees. The WBA likes getting fees.
He had to be in the top 15, so last month (out of the blue) Harrison got the #13 spot (another payoff). Then you can simply put one and one together and Haye/Harrison (HaHa) is made.
So they can get a sanctioning fee. Pretty obvious really. This is the organisation that has Sturm as Super Champion, Golovkin as Interim Champion and wants to have another two fighters box to vie for their vacant "Regular" title at 160. These people are shamless and sanctioning Haye-Harrisson as a title fight probably isn't the worst thing they've done today.
Looking at the WBA's recent Heavyweight 'world' title fights, this actually looks one of their best on paper.. http://boxrec.com/title_search.php?title=WBA&division=Heavyweight&SUBMIT=Go