Can safe gelatin raw materials get infected with BSE in a production plant during the production process if BSE infected raw material was used at some point before?

Absolutely yes. BSE is not a germ - it is a crystal. If processing tables, equipment, storage areas, or tubing is not thoroughly cleaned of all crystals, new Gelatin materials can pick it up. Heat and disinfection are ineffective in preventing BSE. It is not living, so it cannot be killed.