As you suspected, according to the LV Modeller web site, it is on the Lehigh and Lake Erie branch. See
http://www.anthraciterailroads.org/lvrr ... nch-lines/" onclick="window.open(this.href);return false; near the very end of the page. 1.5 miles west of Tifft Junction.
I also found a track chart from 1952, updated 1970. It shows "Clinton St interchange" at that location (Scroll down to page 2b web page).
http://www.marjum.com/lvrr/LVRR-bp-Lehi ... Branch.pdf" onclick="window.open(this.href);return false;. Interchange to what is a good question. Clinton St is just south of I-190 by the I-90 junction.
From some old Conrail Buffalo area track chart I have from 1978, it looks like a connection to a siding parallel to the Lehigh and Lake Erie main back to Tifft Junction. Doesn't answer why it is called "interchange" though.