Ijaw Youth Council (IYC) has condemned the subpeona by the Federal High Court sitting in Abuja on former President Goodluck Jonathan. (dailypost.ng)
I may be misreading your second paragraph, did you mean that the witness is only required to answer under subpeona, but under subpeona are only allowed to refuse to answer if the question would require dislcouse of privileged information or violate a 5th Amendment right? (law.stackexchange.com)
The time line: If the client firm is answering a subpeona, for example, and are on a tight deadline to respond, they may need the document reviews to work fast. (lawyerist.com)