C:\>for %I in (a: b: c: ">:" "&:") do @echo %~fI
C:\>pushd c:
C:\>set "

the output is:

=&:=&:\

=>:=>:\

=A:=A:\

=B:=B:\

=C:=C:\

....



Will not work if there's path attached to the mimic drives in the for set or if the "push ." (cd . also can be used) is skipped.
Looks like the parameter expansion splits the paths in two parts - drive and the rest of the path and later concattanes them.
And used drives are stored somewhere  - and if there's no path part they are not deleted. CD and PUSHD resets drive variables.
