I'm not sure what you mean by "pass each other"...
Pretend, at one point, our universe was as big as the ball labeled with the BLUE number one. For now take it for granted that we're expanding so we know that eventually we'll get as big as the ball labeled BLUE number two and then BLUE number three. Do we agree on that?
Now if we reverse time from BLUE number three (but because we're reversing time I'll call it RED number one now) we go back to RED number two and then RED number three...so this is where we just were.
If we continue to reverse time then the ball universe will shrink more to RED number four, then RED number five, then RED number six, etc etc etc. It will get smaller and smaller.
From topology, if a ball of whatever size without any holes or empty spaces in it shrinks down small enough then it becomes the same thing as a point.
Since our ball-universe is shrinking down smaller and smaller it would eventually become indestinguishable from a point. Thus there would be no room inside this very tiny universe for things to pass eachother.
If you were to live through the whole ordeal yourself, from RED number 1 through RED number 6, the atoms, particles, and everything else in your body would be infinitely close. The planets would be infinitely close. The universe would be infinitely small. Sort of the opposite of the cold-universe scenario if the universe expands forever...eventually particles will be so far apart that nothing can exist in its current form because the distances will be too great for any kind of particle interactions on the large scale.
I'm not sure if the picture helped or if I just repeated myself but I broke this one up into paragraphs so, because I'm not quite sure what you mean by "pass eachother" maybe you can point me to which paragraph I assume that they're not...sometimes the internet is a pain for explaining things so bear with my attempts.