Hi!
I don't know of any specific companies that are -91 and flying -135, but I know that a lot of them still are, and often the FAA Regional Offices and/or the FSDOs and/or local FSDO personnel know about it and do nothing.
I have also read about guys that call this stuff in to the FAA HQ, and nothing is done for months and months and months.
Not very nice!
cliff
GRB