Interesting, but what sort of action would this be?
I'm not sure what Tuck had in mind, nor am I any lawyer, but the basis should probably be something like the "innocent owner defence" in asset seizure.
See: 18 U.S. Code § 983 - General rules for civil forfeiture proceedings
http://www.law.cornell.edu/uscode/text/18/983d) Innocent Owner Defense.
It seems to me it would be easier to conduct a freedom of information act request on information regarding Mt. Gox's customers Bitcoins. This information should not give away anything about ongoing criminal investigations and should be accepted. It would simply request different bureacracies such as the FBI or other likely involved agencies to release information as to the whereabouts and/or ownership powers over customers' Bitcoins. Gets rid of the step of a legal case against the government which could take years.
After the request gives back information you would know whether the story is true or not, and the government would be able to continue its investigation, so it should be an easier way then forcing it to court from the get go.