I'm using paired SOLR queries right now to get taxon counts for different entities, and hoping to be able to use BL for that soon:
select/?q=%3A&facet=true&fq=subject_closure:%22${nodeId}%22&rows=0&wt=json&facet.mincount=1&indent=on&facet.sort=count&facet.pivot=object_category,object_taxon
select/?q=%3A&facet=true&fq=object_closure:%22${nodeId}%22&rows=0&wt=json&facet.mincount=1&indent=on&facet.sort=count&facet.pivot=subjectKey,subject_taxon
From @DoctorBud
Note: This is critical for Monarch UI development