Guitarpima
I always just did tempo changes to slow it down and reset it when the fermata has lasted long enough. Not and exact thing but it works for me.
Some Googling indicates that Sibelius does this as well, but apparently there are cases (versions?) where it will put the tempo changes in a track other than track 1. MIDI type 1 files actually have 17 tracks where the first one is supposed to be dedicated to key signature, time signature and tempo information. Apparently some other MIDi players support having tempo changes in other tracks but it's outside the standard and SONAR does not.
I would have expected that to result in a project that shows notes on the musical grid and is just missing the tempo changes that produce the fermata. So I'm not sure why notes after the fermata would be shifted later in the timeline, but anything is possible if the file format is non-standard.
I would check the Sibelius documentation or their forum for more info.