Congressional Budget Office Cost Estimate: H.R. 1039: Probation Officer Protection Act of 2017 [open pdf - 18KB]
"H.R. [House Bill] 1039 would amend current law to allow federal probation officers to arrest a person if there is probable cause that the person has assaulted, intimidated, or otherwise interfered with any probation officers while performing their official duties. The bill also would direct the Administrative Office of the U.S. Courts (AOUSC) to implement rules and regulations governing probation officers' conduct while exercising that authority. Based on an analysis of information provided by the AOUSC about the very small number of arrests that would probably occur under the bill, CBO [Congressional Budget Office] estimates that implementing H.R. 1039 would have no significant effect on the federal budget."
Congressional Budget Office: http://www.cbo.gov/