According to MelodicRock.com, Alex Lifeson will be making a guest appearance on Triumph guitarist Rik Emmett's new solo project RES9 (Rik Emmett Resolution 9), due out later this year. From MelodicRock.com:

... The album ... will not be under Rik's name, rather the moniker RES9 (RIK EMMETT RESOLUTION 9) in it's expanded form. Recently Rik and the other members of TRIUMPH posted a picture of the trio working together in the studio on a song for Rik's album. I can now deliver the news that the trio are recording THREE new TRIUMPH songs for the project. But that's not all. There are some other very special guests on the RES9 project - Rush guitarist ALEX LIFESON and Dream Theater vocalist JAMES LABRIE! There is a lot of effort being put into this behind the scenes, stay tuned for more!

Emmett is a big Rush fan and had a lot of great things to say about Lifeson in this 2013 interview with Glide magazine. Lifeson and Emmett worked together on a couple of projects back in the late '80s, where they appeared together on "Beyond Borders" with the Canadian Guitar Summit (released as a 45 rpm flexidisk included in Guitar Player magazine, July 1987), and also on Hands of Man on Dream On The Horizon: A Tribute To The Olympic Spirit!. Emmett also covered Rush's Red Barchetta for Sonic Reality's Sonic Elements prog rock project back in 2011. The pair were also participants in the Toronto-based musicians workshop GuitarWorkshop Plus back in 2006.