I think the line is briefly covered in the book
Rails of the Silver Gate by Richard V. Dodge and published by Golden West Books. While this book is primarily devoted to the San Diego street system it does provide some coverage on the early steam commute lines in the area.
The book was first published in 1960 and my copy is from the 4th printing in 1965. There are about 20 copies listed by used book dealers on AbeBooks.
R. P. Middlebrook who wrote the piece for the San Diego Historical Society was a long-time San Diego area railfan and photographer.
Brian Norden