They can't gobble them up. They're owned by a single tenant-owned group, RTH (Roxbury Tenants of Harvard), which includes the Mission Park towers and townhouses. Those triple deckers had been bought by HMS in the 60s and 70s, for their expansion plans until voraciously opposed by the community. HMS ended up selling those triple deckers to RTH in 2002.
Ive posted before about how while the mission of RTH to protect their tenants is noble, ultimately, their resistance to redevelopment can hurt the bigger picture and affordable housing goals as a whole. - Here I do think they really should take HMS money for those lots and build and bigger on neighboring parcels - like their own Mosaic on Riverway, or their own stalled project at 775 Huntington. All of those houses are nice enough, but here, their historic value is minimal in comparison to the value of the location.
roxburytenants.org