Biffa gave information, it was upto SP to make sure that information was checked as correct and factual, companies and people lie (deliberate or not) that's why we have Police & Crown.
If Biffa has a company H&S check(s) dump truck policy and it was not adhered the employee could face manslaughter charges if CM body is found where they are currently searching, they will most certainly be sacked for bringing the company into disrepute, failure to follow H&S and cause death is manslaughter - that may mean corporate criminal charges anywhere in the company/group if the H&S processes are/was inadequate.