Various "alley" spurs existed in Downtown LA, this was the name of one of those, which sounds like what you may be referring to. I believe I recall that this one was accessible from both the "Old" coach yard and from the back way up from the "old" UP line to Grand Central Station, which now comes up behind the Times printing plant.

Other spurs, long gone include. the "old" Times spur, and the RR bridge that for many years went to nowhere (crossing the 101 to where the new Federal Building-Federal Jail complex is) just south of Union Station on Alameda Street. Then there was the "rathole" snaking back into the bowels of the City winding through little Tokyo.

The "Street" was worked in the later years out of the Links/River Station, until this shut down in the late 70's and early 80's. The southern part of the "Street" from Olympic to Firestone Park was worked out of J Yard. This segment was worked 24/7 as opposed to the segments north of 25th Street that were only worked at night. The southern segments of Alameda Street have largely been replaced by the Alameda Corridor, and a whole lot of containers.

Alameda Street north in the 70's and 80's still saw produce, beer, paper, newsprint, and even Christmas tree traffic. The "southern segment" of Alameda saw liquor, cigarettes, breweries, can makers, candy makers, food products, including sugar, corn syrup, and molassess for candy makers, flour mills, steel ditributors, tire manufacturing (Firestone) and distribution, glass manufacturing, papaer, newsprint, and packaging. From my work surveying this area for RR usage, in 2010, most of this is gone today, and there are only a handful of tracks industrial spurs that remain in service with active customers.