That recognition amounted to an acknowledgment by the PLO that they will not contest Israel's claim to Beer Sheva, Karmiel, etc., in any final-status negotiations. Which all means that your question became a moot point the moment that the PLO and Israel exchanged those letters i.e. those letters resulted in a de facto (but not de jure) recognition of Israeli sovereignty over those towns and cities.
Roadside bomb kills five border officers in western Iraq (AP)
from the article: The Big Mac Index of the delusion that 'Ariel is part of Israel'