I got my call 11 days ago. They told me that there were only a few possible assessment dates remaining and that I have to send them my favorite one quickly because they were filling up fast.
Still, there is the possibility that some people reject their invitation to Dublin. I guess those empty slots will be filled up with lucky-ones from the "no call no mail camp". As there are so many people in this camp, they will not struggle to find someone who is available in Dublin on the very next day for example. I think they will keep their options open until the first assessment stage is completed on the 27th.
However, please - this is only speculation.
Best of luck!