When tribes take over the legal jurisdiction under federal law that they have had since 1978, the state will not be involved, except if the state goes in and removes a child in Anchorage or one of the big towns, not villages. The State will then notify the tribe and the tribe will take over 100%. The tribe will be responsible for placing the child, either with a relative or in a Tribal foster care. The court proceedings eventually will be handled 100% by the tribe, in a tribal court proceeding. The only thing the State will lose is the Federal money they have gotten for this. It will go to the tribes. 
This ideally" how it is suppose to work. If it works, then the State will be saving money by no longer paying for care, court time, and case workers. 
Time will tell but the tribes in the lower 48 have been doing this for years for the most part, the exceptions being the five other PL280 states. 
Had Alaska not been designated as a PL280, the tribes would be responsible.