This is possible, yes. When defining planet traits (see PlanetTraitDefs.xml or better yet DLC4_PlanetTraitDefs.xml), you add an xml element <ColonizeEvent>EventName</ColonizeEvent>.
Obviously, this must point to an event's internal name.
So, for example, in the Precursor World DLC, the planet with a Thulium Moon (first in the DLC4_PlanetTraitDefs.xml file) points to <ColonizeEvent>ThuliumMoonEvent</ColonizeEvent>, which is located in the file DLC4_ColonizeEventDefs.xml under the internal name ThuliumMoonEvent.
There's a lot of modding involved here between creating the planet itself, the event and the event choices, and then all the flavor text.
I hope this helps!
