I am not terribly familiar with ITC proceedings, so I'm of limited use here.

That being said, I think 45 days is correct. http://www.gpo.gov/fdsys/pkg/CFR-2012-title19-vol3/pdf/CFR-2012-title19-vol3-sec207-115.pdf

"(b) Grant or denial of review.

(1) The Commission shall decide whether to grant a petition for review, in whole or in part, within forty-five (45) days of the service of the initial determination on the parties, or by such other time as the Commission may order."

I'm not sure what happens with regards to the shutdown.

My understanding is that days means actual calendar days unless stated otherwise. I wouldn't want to guess as to what happened with regards to the petition. I'm not close enough to any circumstances that may have occurred and I'm not knowledgeable enough with ITC procedures.