After doing a bit of research, it's hard to say what the answer is.
One clue is that the specs show a power rating for bridged mode only for 8 ohms, and not for 4 ohms. In bridged mode the amp would "see" a 4 ohm load as a 2 ohm load. So that is not encouraging.
Also, these
measurements of the three-channel version of the amp, which is specified identically to the two-channel version in terms of power capability per channel, indicate that the amp falls somewhat short of doubling max power into 4 ohms (498.7 watts) compared to 8 ohms (294.8 watts), based on the 1% distortion numbers. That is also not encouraging.
On the other hand, though, the specified 8 ohm power rating for bridged mode is 4x the rating in stereo mode, which suggests that the amp has robust power supply and current capabilities. Also, I suspect that the impedance of the bass panels is much higher than 4 ohms at frequencies above the bass region. (You might want to ask Magnepan about that). So those factors are encouraging.
Regards,
-- Al