When (or) do ICO tokens go to an exchange?
It is not possible to know such things unless an exchange announces that they will be listing an ICO or if the ICO creator announces that an exchange will be listing an ICO. An ICO being listed is not automatic; humans are involved. In order for an ICO to be listed on an exchange, the exchange operator must manually add it. This can happen either if an ICO becomes extremely large (although there is no guarantee that a large ICO will be listed by an exchange) or if the ICO creator asks exchanges to list the ICO.

The only way to know whether, where, and when an ICO will be listed on an exchange, you will need to follow any announcements from the ICO and from all possible exchanges that the ICO may be listed on.

The same applies for altcoins.