Yes, I have seen many plastic fuel tanks for both petrol and diesel. They are accepted by the Australian Design Regulations and there are no cases of them having to be removed from cars which are sold in Australia. I believe that many of these cars are sold in USA, Asia and Europe, with the same tanks fitted. While the plastic used is not the same as the plastic available for biodiesel reactors, you have not specified which plastics you object to, just "plastic", so I presume that you oppose all plastic tanks and reactors.

While you have posted a photo, you do not give any information on the fire cause or the heating configuration for the oil. That fire could have been caused by anything and while they look like biodiesel processors, they could have been holding anything. The photo's file name indicates that the units were fuelmeister reactors, which IIRC have electric heating elements in them. I have dealt with the safety aspects of electric heating in plastic reaction vessels in my last post.

Regards,
Tony