Yes, you may. Centrally purchased public transport tickets are regarded as a benefit in kind covering travel expenses. For tax purposes (if it concerns business travel expenses), this falls under the targeted exemption, just like a monetary allowance.
The advantage: no individual expense claims, everyone gets the same ticket, costs are known in advance. Disadvantage: you need to know where everyone is travelling from, and late cancellations lead to unused tickets.
Combine it with a clear sign-up procedure with a deadline.