Connect BME280 Digital Humidity/Pressure/Temperature Sensor to remote Arduino based PLC

I plan to connect the BME280 sensor here to a Particle Photon using this shield. The input from the three measured values (relative humidity, temperature and pressure) will then be used to calculate the associated dew point temperature on the Particle Photon.

I wish to then transmit that calculated value as an analog 4-20ma current signal to a remote Arduino-based PLC which accepts this as an input using this module. Is this feasible?

I would also like to enable RS485 Modbus RTU communication from the Photon to the PLC whilst leaving USB communication from the Photon to the PC intact. Would this module do the trick or do I need something else?

Also, are libraries available for these products?

Any guidance would be greatly appreciated and would assist me in making a purchase.