Yes, i is possible to make a tool (a set of tools actually) to import GIS data into Cataclysm.
That site was generated using GIS datasets from https://docs.digital.mass.gov/massgis and rendered with https://github.com/ralreegorganon/cddamap and some other custom made scripts.
Modified GIS data was put into database - https://www.dropbox.com/s/x316veh8ae8xkql/cataclysm-massachusetts.7z?dl=0. This database can be used to generate overmaps for Cataclysm using this Excel file with formulas - https://www.dropbox.com/s/91f19ywf5g1ovyn/MA_Test_V1.xlsx?dl=1 (output is in AW:AW column on data sheet should be put to your savegame - e.g. o.0.0 file).