I was trying to do the same, but without keeping a variable of autocomplete. I walk throught this calling change handler programatically on the select event, you only need to worry about the actual value of input.
$("#CompanyList").autocomplete({
source: context.companies,
change: handleCompanyChanged,
select: function(event,ui){
$("#CompanyList").trigger('blur');
$("#CompanyList").val(ui.item.value);
handleCompanyChanged();
}
});