Mont. Code Ann. § 46-31-204

Every prisoner confined in state prison for a term less than for life who has been lawfully delivered into the temporary custody of appropriate officers of a party state for trial on a charge or detainer based on an untried indictment, information, or complaint and who escapes is punishable by a fine in an amount not to exceed $50,000 or by imprisonment in the state prison for a term of not less than 1 year or more than 10 years, or both. The second term of imprisonment must commence from the time the prisoner would otherwise have been discharged from prison.