Hi David,
Correct me if im wrong, fractional load sharing acts as cell load sharing wherein a cell can distribute its traffic load to its neighboring cell at heavy traffic load scenario.
The percent of traffic cut off can be dimensioned and is dependent on how much traffic you want for a certain cell to carry before it performs handover to its neighboring cell.
For ericsson equipment try to check following parameters:CLSLEVEL CLSACC RHYST CLSRAMP CLSTIMEINTERVAL AND HOCLSACC.
Normal handover ranking still applies for the said scenario.