Recovering "actionable" netlist from GDS II

I'm interested in the extent to which one can recover usable netlist information from a GDS IIfile.

Assuming the GDS II was produced based on [gpdk|gsclib|giolib]045, and the original schematic (or Verilog source) was subsequently lost, I'm wondering if it is possible to recover enough information about the standard cell netlist to attempt redoing the synthesis (Genus) and place-and-route (Innovus) flows (presumably after having made some additional changes/edits to the netlist).

Right now, I can stream-import the GDS II into Virtuoso as a layout view. I can run Assura LVS to compare this against a dummy schematic: even though the comparison itself will fail, the run will produce an extracted netlist from the layout as a byproduct (*.ldb and/or *.lnnfiles, apparently generated via dfIIToVdb).

I dug around the documentation I could find, and while there's a lot of talk about dfIIToVldb, there's nothing on dfIIToVdb, and I'm a bit confused about what the difference might be between the two, and the output they produce.

I'm wondering what tools there exist to then view and/or convert the extracted netlist information (e.g., the aforementioned *.ldb/*.lnn file formats), into either Verilog or anything else that can be edited and passed back as input to Genus & Innovus for subsequent synthesis, placement, and routing.

Also, I wonder if there's a less roundabout way of extracting actionable netlist information (down to standard cells) directly from a GDS II file...

Any advice much appreciated!