Be careful, it's rated at 49 mpge , not mpg. Mpge is a measurement of efficiency for electrical use.
Rather than reading "49 mpge", what you should really read is "1.45 mpkWh". Mpge is a travesty of a unit.
The 4xe is a phev, so if you hop in and do a 300 mile trip without messing with drive modes, it'll basically do the first 20-25 miles in all electric, using 0 gas. After that is up, the gas engine will fire up, and you'll get 20ish mpg from that point forward.
If you ask me what mpg I get, the answer I'll give is about 22mpg, 37mpg, and about 70mpg.
When the gas engine is running, I get about 22mpg. If I go off what the dash says, it says about 37 mpg, because it tries (and does a poor job) of factoring in an equivalent mpg value for the electricity used. If I look simply at the gallons of gas put in and divide by the total miles driven, I get around 70 mpg.
Ultimately, all those values are basically worthless as they reflect more of what kind of drives I do rather than the actual efficiency of the vehicle.