Done a little bit of detective work, with regards to our Jewish friends on train home yesterday. May not be correct but here goes. Forgive the copy and pastes.

Orthodox Jewish wear

In the Lithuanian yeshiva world, many prominent figures wear a black frock coat also known as a kapotteh (accompanied by either a Homburg or fedora hat) as formal wear. In recent years many Sefardi rabbis also wear a similar frock coat. The frock coat amongst Jews is usually reserved for a rosh yeshiva, (maybe also the mashgiach and other senior rabbis of the yeshiva) and other rabbis such as important communal rabbis and some chief rabbis.

Most married male Lubavitcher Hasidim also don frock coats on Shabbat. All Hasidim also wear a gartel (belt) over their outer coats during prayer services.

So they may have been a group of Rabbi's.

Shabbat (Hebrew: שַׁבָּת, shabbāt, "rest" or "cessation"; Ashkenazi pronunciation shabbos) is the seventh day of the Jewish week and a day of rest in Judaism. Shabbat is observed from sundown Friday until the appearance of three stars in the sky on Saturday night. The exact time, therefore, differs from week to week and from place to place, depending on the time of sunset at each location.
Shabbat recalls the Biblical Creation account in Genesis, describing God creating the Heavens and the Earth in six days, and resting on and sanctifying the seventh (Genesis 1:1-2:3).

Shabbat is considered a festive day, when a person is freed from the regular labors of everyday life, can contemplate the spiritual aspects of life, and can spend time with family. Traditionally, on that day three festive meals are eaten (may be reason you saw them with what you thought was a tin beans being eaten) — on Shabbat-eve, at lunch, and as an end-of-Shabbat evening meal.

Most Hasidim wear long coats called rekelekh during the week, which are often mistaken for frock coats but are really very long suit jackets. On Shabbat, Hasidim wear bekishes, which are usually silk or polyester as opposed to the woollen frock coat. The bekishe and the rekel both lack the waist seam construction of the frock coat. That could be why it looked like a half of a coat.

Well that,s my educational post for the year, it probably not any of the above but hope it helps.