well, heh, that's kind of a given
Unfortunately, I don't actually fully understand the statistical analysis that goes on in either of these documents, though I will say that the official vote trend as analyzed by CEPR does have a pretty decent change in trend around the time of the cessation of the vote tallying, though the quick vote trend doesn't (I may want to come back later and take a fresh look at the statistical analyses used once it's not in the middle of researching both documents more heavily, so I can understand what the different methodologies used are.)
When it comes down to how the OAS alleges that the vote manipulation actually went down in terms of data and tally sheets... well, I guess that depends on whether you trust the OAS or the Morales government more.
I do tend to trust these election observers though -- I mean, they're being accused of being US puppets, but without failure whenever there's an election that's being called rigged, the election is taking place in circumstances and in a government that has already stacked the circumstances in some way or another to stay in power; elections don't take place in vacuums. In Morales' case, this came in the form of replacing the judicial branch with a tribunal which, while allegedly elected, has its candidates pre-picked by the legislature (dominated by his party), and then having that tribunal say it's a-ok to go for a fourth term and presumably beyond. For all Morales might have been a genuine champion of a lot of the causes that many people cherish, he put a lot of measures into place to make sure his rule wasn't in trouble, and when THAT starts happening is when it becomes a lot more likely that elections are doctored.