'The pro-Russians and/or their Russian sponsors have shot down Ukrainian planes before'
Yes they have shot down helicopters, a transport plane and a Ukrainian fighter jet, but none of these were flying at 33000 feet.
'Russia provides the pro-Russians with heavy weapons and with trained soldiers'
It probably allows weapons through. The Russian military leader, Stelkov, is apparently in charge of the rebels and he admits that there are volunteer fighters from Crimea, and possibly Russia too, fighting alongside the local rebels. But he blames Putin for not supplying them with enough heavy weaponry and tanks etc.
'Satellite and local media recording indicate that the SAM was fired from pro-Russian occupied territory'
Did you listen to BBC Radio 4 Today's programme this morning. The BBC said let's hear the Russian view and they interviewed I can't remember who. But he said something like Russian intelligence had tracked all radar systems active in Ukraine and that they have the signals or traces or something that two Ukrainian missile systems were active out of the 3 which they have in that area. The BBC said but what about the twitter boasts that the rebels had captured a missile system about a month ago. He said that even if they had that, they would need an air control or air defence system or something to use them because of the sophisticated radar it requires. The BBC said, but the Russian military have that. he agreed and said that so do the ukrainian military. He said that "twitter" reports are not evidence whereas the Russians have the trace evidence or whatever he called it of the exact locations of the radar systems turned on etc. He said let's wait for the full enquiry before apportioning blame.