LMS Bess,
There is actually quite a lot of information available on the Palestine Railways, whether in published or archival form. I suppose it won't be very helpful to suggest that you come visit the Israel Railway Museum, of which I am currently the head, and peruse our extensive archives and library. However, I would be very glad to share any information available, whether on these pages or directly by email: museum@rail.co.il
I also collect information about Egyptian and other Near-East railways, but there is much less published or even archival information available.
I suppose you already heard of Rabbi Dr. Walter Rothschild and his magazine HaRakevet (mostly available online here: http://www.harakevetmagazine.com/), who also wrote the most relevant PhD. Other English language books include:
The Railways of Palestine and Israel by Paul Cotterell (Tourret Publishing, 1984)
Make Straight the Way by Paul Cotterell (Israel Railways, 2009)
Middle East Railways by Hugh Hughes (Continental Railway Circle, 1981)
Allied military locomotives of the Second World War by R. Tourret (Tourret Publishing, 1995)
I personally have been dreaming of modelling local subjects since childhood, but have been daunted not only by relative-scarcity of RTR models and kits but also by the H0/OO conundrum. This is because for most of the 20th century the railways of this country had a mixture of British, American and Continental rolling stock.
The 13t opens are of the standard MoS / WD (War Department) WWII 5-plank type - the picture below, taken at Tel Aviv Station in June, 1944 shows a rake of opens, apparently loaded with ballast. The 7-plank ones lettered PR are of the WWI MoM / WD 12t type, of which c. 1000 examples entered PR ownership, being around half the total stock at the time. (Photo by Zoltan Kluger
There were indeed quite a few rail-served quarries and various other industries and construction sites in Palestine during the Mandate period. The only stndard-gauge operations with its own locomotives before WWII were the Haifa Harbour Works Dperatment and the related Jaffa Port upgrade project (which was isolated from the railways but had an internal SG line). The HHWD opened large qurries in Athlit and shipped the stone to Haifa by rail. The below photo (from the Library of Congress' Matson Collection) shows one of the HHWD group of Hunslet 14" 0-6-0ST, this one being No. 6 of the outside-cylindered batch. Some of these were later sold to the War Depratment and operated some of their many rail-served depots in the region during WWII.