Bus Eireann could be about to cut overtime payments and change the rules for annual leave.
It comes after the network announced earlier in the week that it could be insolvent within 18 months.
The company could also bring in a recruitment ban and prohibit bus charters from outside the firm.
Siptu is demanding the company start talking to their employees, claiming members are being left in the dark.
Reports in today's Irish Times claim the company will introduce radical changes within the next few weeks, in a bid to generate savings of up to €8m.