A modern short wheel base recumbent has a similar wheelbase to a conventional 700c road bike. The hill climbing issue is still the subject of some debate; your peak torque is undoubtedly lower (because you can't put your full weight on the pedals) but there's no obvious biomechanical reason for lower power.
Any advantage an upright bike might have in the mountains is completely neutralised by the tremendous aerodynamic advantage of a recumbent. A good lowracer recumbent with a tailbox has about half the drag of a normal racing bike. Worse still, an upright rider gets almost no benefit from drafting a recumbent rider.
If the UCI legalised recumbents, a team using upright bikes wouldn't even finish the first stage of a grand tour within the time cut-off. Any team using recumbents could disappear off the front of the peloton and would be impossible to catch. In a time trial, there's simply no contest - the recumbent riders could demolish the upright riders without breaking a sweat. To neutralise that advantage, races would need to be organised exclusively in the high mountains with no appreciable amount of flat roads.