thanks for the picture reference.
they do resemble the basic mechanical seats from either E36 or E46 chassis, though I suspect it is the latter, maybe off a E46 320/323/325
that wire is quite possibly from the OC3 seat mat sensor. Dependent on the actual seat, it may or may not come with heated leather. If it is, it is incorporated with the seat bottom leather. Any possible way to find the tag underneath the seat leather? those numbers will help in identifying what those seats belonged to.
ps : the wire you found, was it passenger or driver side?