I know one can list what commands are enabled in busybox with the $busybox command, but I was curious as to which utilities/packages busybox actually can replace (say util-linux, pciutils, usbutils, coreutils, binutils, findutils, etc).
Busybox was designed and implemented to be the only binary in a system. It implements hundreds of binaries.
You could potentially work out a definitive list of packages by 1) taking the full list of binaries that busybox implements from the website, then 2) mapping each to an installed package (such as using
dpkg -S $(which <bin>) on Debian). Some might not be on your system, you'll need to figure those out separately.