Can you drive to the US on temporary Canadian plates?

If this isn't the case am I likely to be refused entry at that time?

I believe you and/or your car are likely to be refused entry if you haven't done your homework ahead of time. The "touring" exemption in the CBP page you linked to really only applies to people who are bringing their cars into the USA temporarily, i.e., tourists. I suspect (but am not 100% sure) that there would be no problem crossing the border in a car with temporary Canadian plates if you were only visiting the USA for a brief period.

However, you are moving to the USA and taking up residence there. This means that CBP is likely to view you as "importing" your new vehicle, and so it must comply with US federal safety & pollution standards, and you must pay any customs duties owing. This page gives a good summary of the process, but basically, at the border you will need to:

• Provide a certification that the car meets US federal safety standards. Some cars sold in Canada are officially certified to meet US federal safety standards as well, but some are only certified to meet Canadian safety standards. It is sometimes possible to get a letter from the car's manufacturer to prove that a car meets US standards, but the link above says that not all manufacturers will provide such a letter. Before you actually buy your car, you would want to check this.

• Provide a certification that the car meets US federal emissions standards. Again, many cars sold in Canada will not have such a certification automatically, so you may need to get a letter from the manufacturer here as well.

• Pay a 2.5% duty on the car (though most cars manufactured in NAFTA countries are duty-free). If a one-way rental is cost-prohibitive for you, then you might want to make sure that you will not be liable for this duty either.

In addition:

• Many states require you to have some kind of insurance to operate a vehicle on their roads, even if you're not a resident there. You will need to have insurance before you enter the US.

• Many US states (most notably California) require additional emissions tests beyond the US federal standards. This could lead to expensive repairs/modifications to your car to get it registered in your state of residence.

• When registering a newly-bought car in most US states, you must prove that you paid the sales tax on it to the state you're registering it in, or pay it at the time of registration. Obviously, an Ontario auto dealer will not pay sales tax to a US state. If you were not a resident of the state at the time of purchase, you're probably not liable for the sales tax, but I would make quite sure of this before moving down to the US.

All in all, I can't do better than quote the last paragraph of the linked page:

If all of the above sounds like a lot of running around (and it is!) then you might want to consider purchasing a new or used vehicle in the U.S. instead to avoid some of steps and potential issues outlined above.

as per the lady in Ontario said to you, you should probably buy/purchase a car such that you can drive it before 10 days going to US. You can take the receipt of purchase of car along with you while travelling. You can drive through the border and if any US people stops you, you can simply show them your Legal car and inform them you will be stamping plate from US itself. Also show them the address where you're shifting to, adding more to your honesty. I don't think they will ask further questions upon this matter once they are convinced.