There will be railroad maintenance between Hamm and Kassel. This will most likely lead to major scheduling changes or the cancellation of trains. However, busses will be provided to account for cancelled or rescheduled trains.
From August 6th – August 19th, busses will substitute trains between Hamm and Soest, as well as between Warburg and Kassel.
From August 20th there will be busses substituting trains between Hamm and Soest. Therefore, the RB89 only runs between Münster and Hamm, and Soest and Warburg.
From Friday, July 15th onwards, IC-Trains for line Köln – Düsseldorf – Dortmund – Hamm – Paderborn – Kassel.W. – Erfurt – Gera are cancelled.
It might make sense to go to Bielefeld or Hannover first and then take a train from there to Paderborn. This might be a detour for participants coming from the East or the South. However, this might save you trouble with the substitution busses.
From Paderborn Main Station you can take the Line 4 and Line 9 busses to get to the "Uni Südring" stop. The busses run every quarter of an hour.