Can creutzfeldt-jakob disease be spread from a blood transfusion?

Yes. Unfortunately, yes. Variant cases of cjd have been transmitted by blood transfusion in the uk.
Potentially, but... The extensive questionnaires at blood drives are designed to screen out specific infections prior to blood being donated. There are a number of questions that are specific to creutzfeldt-jacob disease (similar to but not exactly the same as "mad cow" disease). To date cases have only been reported from high prevalence areas in europe and these people did not receive leukocyte-depleted blood.