you shouldn't have any problems handling those materials together in Premiere. Set the Sony to 720/60P if available, otherwise shoot 1080/60P if available and scale footage down in the Premiere timeline. If 60P is unavailable shoot 720/30P or 1080/30p if 720 is unavailable and put that in the timeline. Export the timeline at the deliverable spec once completed.
Co-President at fourB Productions, Inc.
Blackmagic Cinema Camera, RED Scarlet-X, Panasonic HPX170, Canon 7D
2011 Macbook Pro 17", 2.3 Ghz Quad Core, 16GB RAM
2008 Mac Pro 2.6 Ghz 8 Core, 10GB RAM
AJA IoXT, Blackmagic Intensity Pro, Blackmagic Mini Monitor
Adobe Production Premium CC, Avid Media Composer 7, Final Cut Pro Studio 3