Pan Am interchange with Housatonic

Yesterday (5/31) I witnessed Pan Am deliver a single empty flat car down to the Housatonic Railroad trackage at Derby Junction. (Derby , Ct.). They left it on the
Housatonic line right underneath Rt. 8 . Today I witnessed HRRC bringing down a single empty demolition debris gondola and left it on the north leg of the Y and took the flat car with them back to Danbury.
Some observations are that the HRRC track has been OOS for a number of years with track in bad shape and much brush and trees blocking the track. Some serious work needed to be done to get this track usable again.
Pan Am has not come south of Kerite in Seymour since the 1990's for a revenue move , so this is notable for that reason.
A lot of work and money and time had to be put into this move. A lot more than interchanging a gondola for a flat would be worth. It is not like a flat car could not come from Pittsfield.
It almost seems like this is an operational test or to prove they can to somebody some someplace. I could even begin to guess what is up here. Maybe some one in the group knows something?
One last question: I know there are some paper barriers stopping short lines from interchanging with each other. Does this come into play here and they may be challenging it?
Thanks,
Ed

This might be a move to preserve that interchange point,if PAR was planning to file paperwork to abandon Derby Jct,or
MN was trying to keep PAR honest on Crew Quals on the Waterbury Branch.
HRRC let Derby Jct to Newtown go to seed to Stop P&W from accessing "shared" Danbury customers directly,forcing the P&W to
access Danbury customers via South Norwalk and a run up MN's Danbury Branch.
With Walk Bridge about to be rebuilt/replaced,this might have forced(by ConnDOT) reopening Newtown-Derby Jct part of the Maybrook Line
for freight and emergency access for MN equipment moves.

I never knew that Derby Jct. was an official interchange point. I have seen Housatonic units go through Plainville. Likely the unit was headed to E. Deerfield for wheel work. Beside the impending bottleneck on MN, maybe Housatonic wants and additional interchange point. Now they could have access to the NS network. This could keep CSX honest, as far as rates for cars destined to Housatonic.

It was brought up, but are there paper barriers set up, when Conrail sold the Danbury trackage? Might the interchange have been company material, such as ties from Perma Treat?

Pan Am's website doesn't list the interchange as restricted like it asterisks CSOR and CNZR, which because of Conrail paper barriers can only interchange traffic with PAS from certain branches. So I think the Housy interchange is indeed unrestricted and always has been.

PAS/G have been long time buds.