it is unclear for me what you have configured on the "other" side. On one side, you are using
mbpoll, which is correct - it acts as a Modbus master. On the "other" side, there has to be some software running, which will act as a ModbusRTU slave device.
As I know you use Evok, then the problem most probably lies directly there - the Evok doesn't (and cannot as of now) act as a Modbus slave. Only as a Modbus master.
It is a bit unusual setup, but pyModbus is able to act both as a master and slave. Be aware of the limitation of the RS485 bus as it can have only one master - one initiator of the communication.
And another caveat. Our RS485 have so-called biasing resistors. Those stabilize the bus when no device is communicating otherwise the lines would be just dangling in the air susceptible to pick of EMI noise. From a certain batch of PLC (ca 2 years ago) we have started to add these resistors.
The downside of this permanent biasing resistors is, that they should be present only once on the same bus. And since both PLC have them, the direct communication over RS485 doesn't have to work in some cases because of that. Luckily enough, the RS485 allows all sorts of unusual stuff hapening (and generating) so it might work for you.
Hope that sheds more light on the matter.