1) traffic on pay phones depends where the fones are located, it also depends upon the economics of the region in which they are installed, ie a ‘rich’ area – more people have mobile phones, pay phones dont get used. I dont think it is possible to generalise and give a ‘average traffic’.
2)I calculate 100 lines/channels would be needed from the PBX to support this traffic. This may be considerably cheaper than 1000 lines (1 each per pay-phone) but how will you connect the pay-fone to the PBX? is there a cost to rent lines for this??