Were I a lawyer, I would not pursue a deal without seeing the evidence first. According to the same upthread post, that hasn't happened yet. The quote says investigators have "gone to see DG"... so that can mean anything from he's cooperating with the investigation, to they're desperate to get something before disclosure, and he's saying nothing. I would think that if DG was responsible, any deals or progress would have produced bodies by now.
Here's an interesting article regarding questioning from a defence perspective:
http://www.cbc.ca/thenational/blog/2012/06/what-to-do-when-the-police-want-to-talk-to-you.html
There is evidence of murder. Calgary detectives are no fools. It took two weeks to close the case. The evidence paints a picture from the Liknes living room to the Airdrie acreage.
Police are not desperate, but if they are allowed to speak with the accused, they will be interested in what he has to say (or not say), and his behaviour. Does he still think that he is clever?
Douglas Garland seems to be familiar enough with the law to make ends meet in his favour. He is a potentially a mass murderer. Potentially, he will bargain a 25 year sentence for the mass murder with the possibility of parole after 25 years. Perhaps he can talk himself into a 25 year parole without revealing the location of the bodies ... piggybacking on the other mass murderer that should be given a chance given his youth.