No such command in JUNOS, I am afraid.
May I ask what You are actually trying to achieve? If the task is to pass broadcasts between 2 Ethernet segments separated by routed network, You could do this by using CCC/l2circuit.
CCC/l2circuit will pass broadcasts on Ethernet/L2 level meaning both subnet IP broadcasts (like 10.255.255.255) and "all-1" IP broadscasts (255.255.255.255) will pass. AFAIK, Cisco is not capable of passing both simultaneously, either one or another, so consider it as added benefit of CCC/L2circuit 🙂