Easy.

Check Google Earth or similar.

Or the books of GE, ABB, Siemens & the usual suspects for building power plants.

Or go there and see what's attached to the cable ;->

Europe buys oil from Libya since ages.
No problem there.

You really need to think big.

It's a bonus that Morocco and Algeria are in this project.
These Countries need a decent source of income.

And if East Sahara is wired up, there will be no stopping wiring up Egypt, Jordan
Mauretania, Niger, Chad.

And why don't the Saudis add themselves to that grid?
The Chinese could tap into Taklamakan,
the US surely has some spare desert to make useful.

Coverage:
http://www.t-mobile.de/funkversorgung/inland/
http://netmap.vodafone.de/cover4internet/index.jsp?appprofile=UMTS-Maps
http://www.o2online.de/nw/support/mobilfunk/netz/index.html
http://eis03sn1.eplus-online.de/evportal/portal/umts

Speed:
T-Mobile, Vodaphone have HSDPA 7.2Gb/s, O2 has HSDPA 3.6Gb/s, Eplus has 384Mb/s (UMTS)

Price:
http://www.teltarif.de/mobilfunk/datenrechner.html

As you are only interested in Prepaid, use this link and change the amount of Mb per month at the end of the URL from 310 to what you need:
http://www.teltarif.de/db/res-mobildaten.html?prepaid=1&von=Heimatnetz&mb=310

Can you read German? If so, look here:
http://www.teltarif.de/mobilfunk/

For news like this:
http://www.teltarif.de/tchibo-surfstick-30-euro/news/37951.html