You can iterate over all timelines of an animation and check if it's an http://esotericsoftware.com/spine-api-reference#EventTimeline. Then you can iterate over all Events
in the EventTimeline.
The following code is not tested, but should basically describe what you need:
Spine.Animation animation = ...;
foreach (var timeline in animation.Timelines) {
var eventTimeline = timeline as Spine.EventTimeline;
if (eventTimeline != null) {
foreach (Spine.Event ev in eventTimeline.Events) {
Debug.Log(string.Format("time:{0} string:{1}", ev.Time, ev.String));
}
}
}