Can one long track-light rail be connected to 2 power sources? With two on/off switches - the rail passes by 2 hi-hat power sources. We thought we could then use either switch to turn the lights on/off. Also, how many pendant lights would be safe to use on 3 attached 8' rails? Each rail comes with 3 pendants, but if it is all on one system (with 2 power sources) what would be consisered safe?

If You Are Wanting To Turn On All The Lights With Two Different Swithches, You Would Need To Use Something Like 14/3 W/grd (three Way Wire) Which Has An Extra "hot " Carrying Wire. Sounds Like You Need An Electrician And Only Need To Run From One Power Source.

They do have 2 circuit track, and lighting. Having problem getting link to here, will try later. If situation doesn't allow, you may need to tap off each light.
What ever rating listed is limit, you may have to use less wattage bulbs, or less fixtures.
9 X 60 Watt bulbs=540 watts

Sounds like you will end up with two switches wired in parallel to control the track lighting - right? That means to turn the light off you would have to have both switches in the off position - if either one is on then the light will be on. This will not operate like a traditional 3-way switch (i.e, where either switch can turn the light on or off). If what you really want is a 3-way switch operation, you will most likely have to do some major rewiring.

Second, I don't know the code rules on this, but you would have to make sure that both of the existing hihg hats are on one breaker - otherwise you would have a very unsafe condition.

I agree with MowerMan - get an electrician to help you here.