Enemy #1 to any CX Program is the notion that "It's not my job."
Even though job descriptions sometimes say "other duties as assigned," many employees feel they need to limit their duties to maintain control over work scope creep, or to avoid stepping on the toes of fellow employees. Moreover, labor contracts will often reserve certain kinds of work for only certain positions, and this is often for good reason - such as to protect jobs. For example, customer service agents may object if custodians answer customer questions if the customer service agents feel this takes away from their work. Conversely, custodians may object if customer service agents pick up litter. It is important to understand the reasons for these dynamics and talk openly and honestly with employees about the issues
Ultimately, though, "it's not my job" is anathema to customer experience. When, for example, a train rider sees one of your employees in uniform, they will expect that the uniformed person address whatever issues arise. It doesn't matter whether the employee is in a customer service uniform, a custodian uniform, a security uniform, an ambassador uniform, a survey uniform, or a safety vest. Either way they are the official representatives of your transit system and are expected to answer questions, and may even be expected to take action to address biohazards or call-in security when needed.
One concept that can help bridge the gap is the idea of "incidental work." If a custodian answers occasional questions about how to buy a ticket or where to catch a bus (or refers customers to others who can answer the question), this can be considered "incidental" as long as it doesn't constitute a significant portion of their work. And if it's incidental, it wouldn't be enough to reduce the need for customer service agents, so it would protect jobs.
Conversely, if a customer service agent or someone from the Accounting Department occasionally picks up a bottle rolling down the aisle and drops it in a plastic bag for disposal, this can be considered just an "incidental" part of their work and won't impact the number of custodians needed on the system. So again, jobs are protected.
From a CX perspective, it's powerful for customers to see employees of all classifications pitch in to take care of customer needs. That sends a strong message that your organization and your employees really care. So as challenging as "it's not my job" can be, work in earnest with your employees and their labor representatives to find common ground ... even if just for a pilot period for all parties to gauge impacts ... and give employees the permission, training, and tools needed to step outside their box from time to time and give customers a hand!