Can you run Lion Chief/LC Plus on Atlas O track?

As long as you can supply the correct voltage to the track, I don't know of any reason why they wouldn't or don't run.  The trains don't know what type of track they are standing upon.

LC and LC+ will run on any O Gauge Track with 18 volts of juice. 

I'm not sure I understand your question, but I have a LC+ Mikado, and have run it on our club's modules which have Atlas O 3-rail track. LionChief locos do require a constant voltage on the rails, we have been using either an MTH Z-4000 or a classic Lionel ZW Power Supply with the throttle levers preset to provide a constant 16 to 18 volts to the track. Usually, the LionChief loco is run by itself on that set of tracks, but if the layout is large enough to provide the space and time to avoid collisions, it is possible to run a non-LionChief loco on that track at the same time (but you do need to be careful!). It should also be possible to run more than one LionChief or LC+ loco on the same track, as long as the locos are different and use different controllers. Again, you have to pay attention and be careful to avoid collisions, something that kids might not be good at doing...

Bill in FtL

River City 3 Railers use Atlas track on our modular layout. There are several LC engines in the group. We have run them in conjunction with virtually everything. Conventional, DCS, TMCC, and 2 LCs on the same track. It's a nice entry level product.

Gilly

Several members of our Kid's Club have the LC sets and they run on our layout, all Atlas, with no problems.

Well, you can run at least six at a time on it.  

I can't speak to more than that.