I think it's important not to sling criminal accusations around here.
The fire on 2/13/2010 at 37th and 84th was investigated and ruled to be an accident. I understand that many people are unhappy with what the property owner built after the fire, but it complied with both the Historic District restrictions and the zoning code, and is very similar to neighboring historic buildings.
The 8-story tower between 82nd and 83rd (known as the A&C Palace) replaces some commercial buildings apparently destroyed by arson. As far as I can tell, it was determined to be arson, but nobody was ever charged. Construction on the new building started before the historic district was designated in 1993, but JHBG deserves a lot of credit for pushing the design of this building to look more like the historic district.
In the case of the fire at the Bruson building, the FDNY is investigating. I think we should wait for the results.
The zoning for this site seems to imply a maximum floor-area ratio of 4.8 if some community functions are included in the building (I think this includes medical offices). This would seem to imply that a new building could be one storey higher than the old one if it uses the same footprint.