a) The units set forth in Section 1135.20 are presumptively appropriate. Petitions for units other than those set forth in this Part may be filed and shall be processed in accord with the regular rules of this agency concerning representation cases (80 Ill. Adm. Code 1110). Units of educational employees of the Board of Trustees of the University of Illinois other than those set forth herein shall be established only if the petitioner can show the following by clear and convincing evidence:

1. 1) that the unit is otherwise appropriate under Section 7 of the Illinois Educational Labor Relations Act;
2. 2) that special circumstances and compelling justifications make it appropriate for the Illinois Educational Labor Relations Board to establish a unit different from those set forth above;
3. 3) that establishment of a different unit will not cause undue fragmentation of bargaining units or proliferation of bargaining units. Undue fragmentation of bargaining units or proliferation of bargaining units means that the number of bargaining units is such as to threaten to interrupt services, cause labor instability, and cause continual collective bargaining and a multitude of representation proceedings.