Big Truck:
Never happen in a million yrs,
first problem is not enough traffic crossing to even justify it.
Second who wants to come off a multi billion £ bridge to drive on A75/A77!!!
^^^^^^^^^^^^^
+1
the only way itl ever happen is if they strike oil in donegal and even thats in eire.
theres no industry no infrastructure,desperate poorly maintained roads,no money and no export from northern ireland to keep the ferries going never mind the bridge.
the main reason for the lack of anything over here is because when god make ireland,the let the arabs and the irish decide who was getting the potatoes and who was getting the oil.
they tossed a coin for it and the irish got 1st choice. 
Franglais:
Here`s a couple of figures to get a handle on it.
Channel Tunnel is about 50km long of which 38km is under sea. It goes to 115m below sea level.
Beauforts Dyke is 250m deep so any tunnel would needs be 300m deep? As said a bridge there aint about to happen because of munnitions, apart from the length and depth.
A different place? 80 km rail tunnel Dublin / Holyhead? 2013 prices were £60m per km for rail tunnels. Ballpark guess 5,000 million just for the tunnels?? The channel tunnel cost £4.65 bil in 2001. About £7.35bil today.
So wouldnt a St Georges Channel Tunnel be 7 times more expensive than the Chunnel, even allowing for inflation.
Big expensive engineering whatever.
This is a screen shot of a raster scan of the offical Admiralty chart, the depths are as indicated …
More detail in this one …
if they start building it as a joint venture starting at both ends similar to le chunnel,can you imagine just how many paddys are going to drown digging the foundations■■?
itl surely end in tears the same way the irish olympic water polo team ended up in recent years when they had to come home early after all their horses drowned.
Plus the fact of the wind.The wind!
The British side:Sorry dear people force 12 out there today,bridge is closed.Form an orderly queue for the preceding 64 miles,and then form another orderly queue for your tea and biscuits.
Irish side of the bridge.Blow her on lads,hold on tight,turn up the radio,and may God go with you! 
that would be the way of it though the irish my become influenced by the brits h&s and insist the only trucks heading over should be overweight with a load of hanging over the 20 ton of steel on the floor with happy buttons installed and in full working order so they can cross quicktime.
