Section 196.28 - Summary investigations(1) If the commission believes that any rate or charge is unreasonable or unjustly discriminatory or that any service is inadequate or cannot be obtained or that an investigation of any matter relating to any public utility should for any reason be made, the commission on its own motion summarily may investigate with or without notice.(2) If, after an investigation under sub. (1), the commission determines that sufficient grounds exist to warrant a hearing on the matters investigated, the commission shall set a time and place for a hearing. A hearing under this section shall be conducted as a hearing under s. 196.26. (3) Notice of the time and place for a hearing under sub. (2) shall be given to the public utility and to such other interested persons as the commission considers necessary. After the notice has been given, proceedings shall be had and conducted in reference to the matter investigated as if a complaint specified in s. 196.26(1) (a) had been filed with the commission relative to the matter investigated. The same order or orders may be made in reference to the matter as if the investigation had been made on complaint under s. 196.26.(4) This section does not apply to rates, tolls or charges of a telecommunications cooperative, an unincorporated telecommunications cooperative association, or a small telecommunications utility except as provided in s. 196.205.1977 c. 29 s. 1654 (10) (c); 1983 a. 53 ss. 39, 41; 1989 a. 344; 1993 a. 496; 1997 a. 218, 229; 1999 a. 32; 2001 a. 16; 2005 a. 441; 2011 a. 22. The PSC's decision not to investigate under ss. 196.28 and 196.29 [now s. 196.28(2) and (3)] was a nonreviewable, discretionary determination. Reviewable decisions are defined. Wisconsin Environmental Decade, Inc. v. PSC, 93 Wis. 2d 650, 287 N.W.2d 737 (1980).