Here's one case to cite:
The courts have also recognized the authority and need for the issuance of such an order “The persons who made the investigations can be called as witnesses before the Superior Court, there to testify as to the facts they ascertained…they may require any investigator whose report is before the court personally to appear and subject himself to cross-examination.” Wadell v. Board of Zoning Appeals, 136 Conn. 1, 8, 68 A. 2d 152.
I have noticed many of the cases before the board with DESPP as the opposing party are lost. If this is because they just want to introduce affidavits or reports into evidence then you have a right to request those people show up and be cross-examined. If you don't, you cannot cross examine a piece of paper very well. A simple pleading by DESPP I don't think is enough, they should have fact stating witnesses to support any finding.