Yes! To do this, you need to use field mapping when you do Load Locations (or Add Locations from python). You need to map your input data's break value field to the Breaks_[ImpedanceAttribute] field in your Service Area Facilities layer. Each one will get its own break value that way. The break values option on the layer properties will be used only if a facility doesn't have its own in the table. In other words, the values in the table override the default value on the layer properties, which is just what you want. You can read more about field mapping here: http://resources.arcgis.com/en/help/main/10.2/index.html#//00470000003t000000