Wait/Result can expect OperationCanceledException as its AggregateException.InnerException, regardless of how the cancellation was done.

UnitTests.cs

using System;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.VisualStudio.TestTools.UnitTesting;

[TestClass]
public class WaitCanTreatInnerExceptionAsOperationCanceledException
{
    [TestMethod]
    public void CancellationTokenPassedToStartNew_CanTreatAsOperationCanceledException()
    {
        var cts = new CancellationTokenSource();
        try
        {
            cts.Cancel();
            Task.Factory.StartNew(() => { }, cts.Token).Wait();
            Assert.Fail("Wait was expected to throw.");
        }
        catch (AggregateException exception)
        {
            var ex = (OperationCanceledException)exception.InnerException;
            Assert.AreEqual(cts.Token, ex.CancellationToken);
        }
    }

    [TestMethod]
    public void CancellationTokenObservedByDelegate_CanTreatAsOperationCanceledException()
    {
        var cts = new CancellationTokenSource();
        try
        {
            cts.Cancel();
            Task.Factory.StartNew(() => { cts.Token.ThrowIfCancellationRequested(); }).Wait();
            Assert.Fail("Wait was expected to throw.");
        }
        catch (AggregateException exception)
        {
            var ex = (OperationCanceledException)exception.InnerException;
            Assert.AreEqual(cts.Token, ex.CancellationToken);
        }
    }

    [TestMethod]
    public void CancellationTokenObservedAndPassed_CanTreatAsOperationCanceledException()
    {
        var cts = new CancellationTokenSource();
        try
        {
            var task = Task.Factory.StartNew(() => { while (true) cts.Token.ThrowIfCancellationRequested(); }, cts.Token);
            while (task.Status != TaskStatus.Running)
                ;
            cts.Cancel();
            task.Wait();
            Assert.Fail("Wait was expected to throw.");
        }
        catch (AggregateException exception)
        {
            var ex = (OperationCanceledException)exception.InnerException;
            Assert.AreEqual(cts.Token, ex.CancellationToken);
        }
    }
}