When Baltar and the Cylons come to Galactica above the Algae planet he says:

"The chances that we've all converged on this small planet at the same time are infinitesimally small. So we all understand it's not chance."

Gaeta also says:

"I can't get my head around these odds. That both humans and Cylons both converged around this planet at this exact moment, just as the star's about to go supernova?"

And the coincidences are indeed extreme. Particularly if you imagine that it all had to be planned thousands of years ago to take place right when a nova would go off and activate the temple. (Pretty extreme way to activate your temples, though.) Gaeta makes almost exactly the same observation, noting he is not much for religion but even he can't get his head around the odds of the nova happening the same day.

But here are the events needed to make that meeting happen, all of which had to be roughly timed to meet the approximate predicted time of the Nova, and then more carefully timed as that event could be more accurately predicted.

• The war itself
• The creation of the Cylons and the first war, which lead to the later war
• Baltar's path, driven by the 6 in his head.
• Baltar being on board the base ship
• The babbling of the hybrid, interpreted by Baltar, that leads the Cylons there
• The contamination of the food forcing the fleet to go back to the planet at that exact time
• The hard journey through the radiation field, only plottable by Cylon Athena
• Tyrol's compulsion to find the temple
• D'Anna's compulsion to go to the temple and see the five
• The timing of the cylon occupation, and then the exodus from New Caprica
• The nova itself

In some ways it almost makes it easier if you decide that the powers who planned the meeting had some ability to trigger the nova under their own control. It's debatable which requires more fantastic ability -- control over the death of stars, or manipulating entire civilizations to bring them together at a meeting planned long ago.

The timing need not be that exact. For example, one might consider the star giving off rumblings which would allow advanced beings to get a closer and closer estimate for its time of explosion. The Exodus could then happen near that time (within a year or two) and the fleet pushed to settle on a planet until the time is ripe to leave. It's much easier to control when they leave. Even so, they left too early, and passed the Algae Planet, and had to have their food contaminated in order to take them back there.

Bringing in the Cylon forces was much easier, it simply involved timing a message to the Hybrid, and having Baltar on board to interpret it. Though it's not fully explained just how they know to come to this location just because Baltar interprets the line about the "Eye of Jupiter." Have the Cylons always known where the Eye of Jupiter was, just not knowing it was a clue to Earth?

All of these events give strong evidence that powerful beings are manipulating events. This was always required by the Peter-Panesque mantra that "all this has happened before, all this will happen again." Without time travel, prophesies and cycles don't happen unless they are made to happen. But we still no little about who these powers are and what their motives are. The only ones we know are the Final Five, possibly associated with their God.