99% of brush guards & bull bars mount to the frame, replacing the front tow hooks as they use those mounts. That said, the Expedition tow hooks haven't moved since 2003. So any guard 2003 and up should fit. The fascias have changed a few times since 2003, but not the underlying frame. Atleast for the most part the frame is largely unchanged.
F150 frame shares nothing with the Expedition - its not a stretched or modified version, etc. So I would be surprised if the width between the two is the same, which is the key to grill guard applications. Even if it were the same, the F150 has a hood with integrated grill. That design calls for F150 guards to pushed further forward in the center in order for the hood to open.
The only trouble you might run into is guards which have upper support brackets that mount to the radiator header panel. Often these can be omitted.
My local county Sheriff Dept has 2015/2016 Expeditions as well as 07+. They all appear to use the same push bumper attachment, if that helps any. I thought they were Go Rhino, but their website doesn't mention Expy.