If that's the case, then any possible scandal here would be squarely on the company selling the vehicles - not FedEx.
FedEx might just be a tacked-on name. You see that quite often with Prop 65 cases. The plaintiff attorneys add anyone even remotely related to the case, just to drive up pressure and chaos, hoping for quicker/larger settlement offers.
In this situation, even if FedEx has nothing to do with vehicles sales, they might opt to settle and write a check just to make the bad publicity go away. If you think that sounds like a shakedown, you'd be right.
I do doubt FedEx would be in any way involved in the details of selling leased vehicles. I can say with a high degree of confidence there never was a meeting with FedEx execs where they pitched the idea of increasing residuals by swapping odometers...
A project to cut an ongoing vendors costs is about the only way for a large cap procurement specialist to meet and exceed targets with no possibility of additional valid free market bids. That opens them right up to questions of liability, with managers knowing or avoiding knowledge, workarounds, special advice to other divisions, etc.
You don't have to go to jail to lose a lawsuit.. I worked for a company that put together a whole system for reporting these kinds of ethics irregularities in the companies favor. I don't think that was a charity, they act as a defense or at least lower punitive damages a judge is likely to award when violations still occur.
Say the lawsuit is originally against just Holman Fleet Leasing and FedEx is the one legally liable (Maybe FedEx is the one that is doing something naughty. Maybe there's some contractual language around Fedex assuming all legal liabilities for the vehicles sold.). You're going to spend a bunch of time in court arguing with Holman about if they're even the right party to sue, and your case is either going to get thrown out or you're going to lose. Meanwhile, the statute of limitations is still ticking, so if it takes a long enough time to adjudicate the case against Holman, you won't even be able to refile the same case with the correct respondent. Oops. but if the statute of limitations miraculously hasn't run out yet, that's not even considering the possibility that the kind of person who would roll back an odometer would also have a punishingly short document retention policy, so all the documents that still existed at the time you filed against Holman have long since been shredded and destroyed, so your discovery in the new case against Fedex is going to be a single email saying "yeah, we don't have anything going back that far. Oops again.
Now consider the lawsuit filed initially against both Holman and Fedex. Assuming your list of respondents is complete, the case isn't going to get thrown out because you sued the wrong person. Liability will still be adjudicated (and the case amended to drop respondents as the proper liability holder gets determined), but now you don't need to worry about the statute of limitations running out as you wait for the determination of liability against the first respondent. And the document retention clock starts with that lawsuit and covers the time where you're just determining who hold liability, so now they can't delete those documents even if they other wise would be. Both of them are now going to be legally required to retain all the stuff you list in discovery for the duration of at least their involvement in the case. Sure, they could destroy those records anyway, but that sort of thing is regularly used to infer guilt of the respondent with the worst possible inferences when it's destroyed in violation of discovery.
I've learned over time, it doesn't matter how righteous your defense is - all that matters is the money it'll cost to make the issue go away. Turns out, it's almost always cheaper to write a check than defend yourself.
A company the size of FedEx has accountants and actuaries watching leases of this scale like hawks. It's simply not believable that Fedex never "noticed." And if they noticed they were getting much better than normal resale values but didn't ask why, that's very much the definition of complicity.