They post the ice charts pretty much every day on this blog, although I'm not sure how to interpret it, other than red is bad, but I'm not sure what color they can crunch through.

The blog covers stories of different boats trying to make the transit. They aren't talking about the Silversea Explorer, but they did a post a couple of days ago on the Bremen, another cruise ship (sister to the Hanseatic), that plans to cruise part of the Northwest Passage and then sail back to Greenland. Today's post advocates Canadian icebreaker support and references:

"There are some 14 private yachts staged at east and west strategic anchorages looking to make a Northwest Passage transit. There is a tug towing a salvage barge from Norway enroute to salvage and transport Amundsen's ship named MAUD from Cambridge Bay back to her homeland of Norway. And lets not forget a commercial passenger cruise ship scheduled to transit the Passage from Pond Inlet to Cambridge Bay and then exit back to Greenland."

http://northwestpassage2014.blogspot.com/

Position of Explorer at Pond Inlet shown with the blue arrow.