Spectre itself doesn't have a method to directly write CSV, although you could write a VerilogA model that wrote out CSV.
The easiest is probably to open the data using ViVA (from IC613) or wavescan (from IC5141) and that allows you to save selected signals from the results browser to CSV. In wavescan it is File->Save Signal and in ViVA it is File->Export.
It's also possible to save to CSV in simvision (that will work if the results are in SST2 format which simvision can read).
Regards,
Andrew.