Maybe the reason your station goes to 1080i for the news is because they are using the equipment they had before fox started doing hd. Is it actual HD or just upconverted? My non hd upn sends out 1080i and is owned by fox.
As JohnH posted, I am talking about WRAL 5 for CBS and WRAZ 50 for FOX in Raleigh. WRAL was the first to go HD in the country way back when... and several years ago they built a new HD newsroom. They also have mobile HD cameras they take out for location shoots for news segments.
The 11:00 news is on WRAL, they have a 10:00 "early" news on WRAZ... and though they sometimes rotate the news persons around, its basically the same people and exactly the same newsroom.
Though I don't like hockey... they sometimes broadcast 1080i HD Hurricanes games on WRAZ during the hockey season (when hockey exists of course). And last year they doubled-up on the NCAA broadcasts so they could show an HD game on WRAL and another HD game on WRAZ when two of the local teams were playing games at roughly the same time.
So they take advantage of their 1080i equipment whenever they aren't broadcasting the FOX-forced 720p programming... which is kind of nice.