I believe German subsidiaries of American insurance companies could also access information on the cargoes of specific cargo ships as well; some of the officers of torpedoed ships were shocked at how much the U-boat officers knew about the ships they were sinking...
Well, I know that most U-Boats carries a Lloyds of London maritime book showing all the world’s merchant vessels (practically all were insured by the company). Rather convenient for ID-ing your potential target. I rather doubt they had time-sensitive info like accurate cargo manifests. Even if Intel could get that stuff, just getting it to the U-boat skipper before he sailed? Seems unlikely.