I grant I am at a distance, but the PA strategy for the last two years appears to have been "show maturity, isolate Israel." Unlike Arafat, who was a corrupt thug who never really wanted an independent state because it would mean they actually had to start governing, Fayyad has been pursuing a policy of actually creating a state. Fayyad has also hit on what looks like a strategy with a reasonable chance of success because it bypasses the traditional players and takes advantage of the reduced power of the U.S. (and EU) as power brokers. Recognition by Brazil, Turkey, India and China and the Arab League, combined with a significant smattering of regional players, will have significant impact and real world consequences even if the U.S. and most EU countries hold out and the U.S. blocks recognition in the U.N.
Hamas, for its part, seems to be angling for a seat at the table for re-integration when that occurs. If Fayyad is successful, it would result in the possibility of a reintegration of PA and Gaza in which Hamas takes part in the government with the blessings of significant international powers, who would then pressure Israel and its allies to accept a fait accompli. All this could be achieved without either renouncing the right of return, or even renouncing violence against Israel.
But that doesn't work if the PA and Gaza fall back to the old ways of bombings. Brazil, India and China are not going to embrace a country that still looks like a terrorist state (at least not without natural resources). So who conducted the bombing?
A few possibilities suggest themselves:
1. Hamas or Hamas factions who believe that the Fayyad plan would result in Palestinian recognition of Israel and a permanent end to conflict without destruction of the "Zionist entity."
2. A new organization of Israeli Arabs sympathetic to Palestinians.
3. An Israeli organization seeking to discredit the PA and/or provoke armed conflict.
None of these really makes sense or feel right. Possibility #1 seems most logical, but it is not clear how they get past security. The next most likely possibility is a combination of #1 and #2. Hamas or a splinter faction may want to maintain Hamas' current cease fire to get a seat at the new table run by the BITC Group (Brazil, India, Turkey, China), while hoping to provoke a confrontation that would discredit Fayyad.
The problem with #2 is that I would expect any new org to want to claim credit. The problem with #3 is that I would have expected some sort of claim of credit in the name of some militant Palestinian group.
Hopefully, further investigation will prove fruitful.