Here: http://www.ontarioimmigration.ca/stdprodconsume/groups/csc/@oipp/documents/document/oi_app_guide_phd.pdf you can see that international Masters or Phd graduate class requires overall of 7.0 or higher on IELTS. You can find other forms and guides at http://www.ontarioimmigration.ca/en/pnp/OI_PNPFORMS.html but I found no mention of IELTS under the regular worker stream or international student with job offer stream.
As for Canadian experience class where you are posting your topic under, it doesn't matter if you are in Ontario or somewhere else because Canadian experience class is federal and has the same rules in all provinces. The requirements for them are Benchmark 7 for skill type 0 or skill level A workers and Benchmark 5 for skill level B workers. Benchmarks translates into IELTS scores like this:
NOC CLB Levels Test results for each ability
Speaking Listening Reading Writing
0,A 8 6.5 7.5 6.5 6.5
0, A 7 6.0 6.0 6.0 6.0
0, A, B 6 5.5 5.5 5.0 5.5
B 5 5.0 5.0 4.0 5.0
B 4 4.0 4.5 3.5 4.0
To get Benchmark 7 for example, either all of your scores should be CLB 7 = 6.0 or higher or it is ok if you have one from CLB 6 if you have another one in CLB 8.
You can read about this in the application guide for CEC at http://www.cic.gc.ca/english/pdf/kits/guides/5609E.PDF
