Several of the blogs (e.g. Paleojudaica, Textweek) reference this interesting article in Bible and Interpretation. Thanks too to Mark Elliott for alerting me to it:
The Nature and Origins of the 1st-Century Synagogue
It is very likely that the institutions referred to as proseuchai in inscriptions dating from 3rd and 2nd century bce Egypt were, in fact, Jewish temples, and not synagogues as is commonly assumed.
By Anders Runesson