There's a universal tool for the classic NFS titles Hot Pursuit and High Stakes called NFS Wizard that can open sound bank (BNK) files and extract samples from them, but unfortunately it cannot open many of the files, including cop speech files. It also crashes when opening Porsche Unleashed BNK files.
There are also CTB/LTB files in High Stakes as well as CCT/CLT/ECT/ELT files in Porsche Unleashed. Those are sound tables which work similarly to the AUD files in rFactor.
The idea would be to write an unpacker/repacker for the BNK files as well as a decoder/encoder for the sound table files, but I lack the expertise to do so. Would anybody be willing to help?
There's a detailed explanation of the sound formats here: https://www.extractor.ru/articles/electronic_arts_audio_file_formats_description/
I've attached various example files to the post.