It is my understanding that for many years Cuba's connection to the rest of the world was via an old tropospheric scatter system to Florida, operated by AT&T. The US embargo had an exception for existing telecommunications communications systems. This continued until Hurricane Andrew destroyed the Florida antennas in 1992. There was no financial justification to rebuild the system. Since then Cuba's main links to the rest of the world have been via satellite. However, the cables you mention are a possibility.

If the cable from Fla to Yucatan is not new, there would be little reason to try to run a branch to Cuba. Much easier and better to run a new cable. However, even if the US was willing, the Cubans would probably rather deal with someone else.

I also recall reading somewhere that one of the major reasons that the US invaded S.E. Cuba in the Spanish-American War is that was where the telegraph cables to Spain came ashore.

ETECSA (Empresa de Telecomunicaciones de Cuba S.A) used to have offices in Jose Marti airport in Havana(terminal 2 or 3). You could get a local prepaid sim card with the following rates: http://www.etecsa.cu/index.php?page=...cubacel_tarifa

Rates are in convertible pesos (CUC) that are pegged to the US dollar. There will likely be a 10% fee to convert USD to CUC. Credit cards with US banks probably will not work in Cuba due to embargo restrictions.

Local rates are .35 CUC peak (7 AM-11 PM) or .10 CUC off-peak (11 PM-7 AM). Rates to North America are excessive at 1.60 CUC. In theory a callback card could be used in conjunction with the local number but the combined rates would be the same or higher for many callback cards.

Other options I can think of would be (and all are expensive):
1. International callback sim card.
2. VOIP but internet is costly and latency pretty bad due to satellite back-haul mentioned in other posts.
3. Low tech local calling card but international calls to US have rates that aren't much better than a local sim card.
4. A prepaid sim card from a country other than the US that has Cuba roaming capabilities (e.g. Digicel), but rates will also be pricey.
5. Use a satphone that doesn't block calls from Cuba due to US embargo restrictions. Would likely be cheaper than other alternatives on a per minute basis.

Drop "off the grid", enjoy the music, drink plenty of rum punch and don't worry about it until you leave Cuba?