The Cairo talks left Hamas with its tunnels, labs, weapons factories, drones and with the Izz ad-Din al-Qassam Brigades and their naval commandos. In fact, Hamas's military wing remains as it were—under the direct and exclusive command of Hamas.
This is why Israel views the agreement signed on Thursday as one that has no chance of being realized, so there's no reason to even waste energy on trying to sabotage it. Especially as both the American administration and the Egyptians have asked Israel not to interfere.
Nevertheless, the agreement does indicate some change in Hamas's willingness to give up its monopoly over arms in the strip. For example, the responsibility over border crossings will gradually be transferred to the Palestinian Authority. Some 3,000 policemen are set to be transferred from the West Bank to Gaza and join the 12,000 existing Gazan police officers, who will also go under the PA's purview.
The manner in which these moves and others will be carried out will be determined in discussions of joint Fatah-Hamas committees. In general, most of the articles of the agreement signed on Thursday are dependant on the work of these committees, and there are no deadlines for most of the planned changes. For example, the future of the Gazan government bureaucrats will be discussed in a committee due to issue its recommendations in four months—an eternity in the Middle East.
Another committee is supposed to present a plan to put an end to persecution and arrests of Hamas members in the West Bank, which will theoretically require Hamas to announce a halt to terror activity. But there is no mention of such a provision in any joint Hamas-Fatah document, and the information the Shin Bet currently has does not indicate a decline in the activity of Hamas's West Bank militant cells, quite the opposite.
Israeli officials believe the fact Abbas acquiesced to the Egyptians, and his willingness to accept an agreement that does not give him control of the weapons in the strip, only perpetuates his position as a lame duck.
Furthermore, his need to present himself to the Americans as a leader who has the mandate to act on behalf of the entire Palestinian people is more important to him than short-term concessions. The US is about to present a diplomatic plan for an agreement in the Middle East, and presenting himself as a legitimate partner is of utmost importance to Abbas.
Either way, Israeli officials don't believe Hamas would take on the commitments the PA has towards Israel. Their assessment is that the agreement would collapse within three or four months.
In any case, the Israeli government would not be able to live with this agreement, even if it includes a Hamas commitment to the PA to lower tensions in Gaza. Such an agreement would require Israel to drop its policy of treating the Gaza Strip and the West Bank as two separate entities, which has so far allowed it to avoid going into diplomatic talks, claiming Abbas does not represent the entire Palestinian people. This is something Israel would not be willing to give up so fast.
Furthermore, Israel would not receive any guaranteed achievement in return for such a concession, such as Hamas recognizing Israel or a commitment from the Palestinians to stop the acts of violence.
Therefore, this agreement will likely not be able to hold water.