Frank, funny you mention this.
I was digging into the same thing about a year ago and posted on the Pennsylvania Railfan forum. I hope the link works.
https://www.railroad.net/rail-mileage-b ... l#p1593585
I was responding to a thread on the railroad distance from Reading to Jim Thorpe (Mauch Chunk) when I found the same line you are talking about (using the Hauto tunnel at Lansford) from Mauch CHunk to Tamaqua. It used the CNJ east of the tunnel and the Panther Creek RR (later Lehigh and New England) west of it.
It lasted at least as long as 1909 - here is the timetable in the Official Guide. Go to page 424 in the pdf (316 as the printed page number in the Guide)).
http://cprr.org/Museum/Books/I_ACCEPT_t ... e_1910.pdf
I am probably not remembering the details right, but the service might have ended very soon after 1909. I think it maybe have ended to the parents companies of the Panther Creek RR and of the CNJ having a falling out, perhaps because one got a new owner. (CNJ in PA was the Lehigh & Susquehanna RR , which I think the CNJ leased from the Lehigh Coal and Navigation Co (LCN). The Reading gained control of the CNJ around this time - not sure that was relevant to the end of Mauch Chunk to Tamaquq service or not.
Although I think passenger service through the tunnel indeed ended not long after 1909, freight (coal) ran much longer, to the late 60's when the tunnel shut down.
Jim S
