Here's a graphic (from the UK Daily Mail) that shows Cueta and its surrounding territory.
This is not a "physical" part of Spain, no way, no how -- rather, it's just some territory hanging off the coast of Morocco.
As such, it's probably an exercise in futility for Spain to think of "holding it" for the long-term. Particularly in light of the reality that in Europe, islam (and islamic jihad) is "on the march".
Looking at the graphic, it appears that "the border" that was originally breached isn't in the town of Cueta, but is in fact a little "distant". It also appears that there is a substantial length of "border" that Spain must defend against Morocco.
If the Moroccans (or the hordes) decide to assault it, it's over for Spain there...
