Interesting that you doubt the official story supported with video but u do believe unsupported claims by unreliable sources!
What is the Syrian Observatory of Human Rights? Did you check it before? It's a one man show office, same goes for the Syrian League for the Defense of Human Rights?
Reuters reporter Oweis was expelled along with other media from Syria by govt for fabricating videos, doing montage on videos & even putting words in victims mounts, asking a wounded soldier in one instance to say that he was shot by a security officer for not shooting the protesters & the wounded soldier shouts in pain it's not what happened & at the end the footage was distributed without the words of the soldier, only the words of the professional reporter.
I would stick with the story that provides more info & until the govt let media back under a new media law, keep some credibility for your agency by confirming resources before posting articles.
Hundreds of military & security personnel can only be killed by organized terrorist mobs with external and internal support backing them with money, weaponry, communication & logistics; I have one hint in mind: Foreign Intelligence Services with similar history, try CIA for instance creating local mafias especially playing on sectarian sensitivities.
The link to the article and our comment if it's published by the moderator: http://www.dailystar.com.lb/News/Middle-East/2011/Jul-23/Syrian-train-derailed-near-Homs-several-arrested-reports.ashx#axzz1SyANU8hc