Triple-Tracking CN's Kingston Sub

According to VIA's web postings on the government-financed infrastructrue upgrading, 41 miles of third track are being added on the Kingston Sub. and turnouts on all ends will be replaced with #20 turnouts.
I don't understand why the turnouts are being upgraded. Wouldn't the VIA trains typically stay on tracks 1 and 2 and the freights that are being overtaken be switched to the outside track(s)?
Also, what is the govt.-financed work accomplishing at Brockvlle in relation to the station platforms? I have been there once and seem to recall there was a platform on the north side for TK 1 and an island to serve TK 2.

Andy

For the most part it will be the turnouts at existing crossover locations that will be upgraded to #20 from #15 or less. There is no need to replace turnouts at the start/end of the third track since these will be new installations. Regardless of whether the VIA trains or freights change tracks, higher permitted speeds will keep things flowing better for everyone.

As to platform and other changes at Brockville, some more detailed information can be found here.

Trains at Brockville are now only being served via the North track. The island platform is gone and the South track platform hasn't even begun to be built yet.

The Oshawa and Belleville trackwork is done with the island platforms in service.

Cobourg's island platform has yet to be put in service as well.