The general rule for trusts is they're subject to taxation at the top marginal rate on all of their income. The two exceptions to that rule are qualified disability trusts and graduated rate estates that arise when an individual dies.
For qualified disability trusts, as you pointed out, the policy is that these are trusts that are set up to support a disabled individual. They are therefore provided access to the graduated rates and not the top rate of tax, which was 29% last year. Under Bill C-2, that would be 33%.
The access of a qualified disability trust to the graduated rates is predicated on the income of the trust being paid to an eligible beneficiary, someone eligible for the disability tax credit. If ultimately there has been income accumulating in the trust that has been taxed at these lower rates, and income is later paid to someone who would not be entitled for it to continue as a qualified disability trust, then the rules have what is called the “clawback” of the graduated rates. This essentially provides an additional tax in respect of the lower rate in previous years, where an amount has ultimately been paid out to a non-qualifying individual.
This would prevent, for example, a qualified disability trust from being set up notionally in support of someone who is actually disabled and who would normally qualify, but then, after earning income in the trust for a number of years and taking advantage of the lower graduated rates, ultimately being paid out to someone else—perhaps the settler of the trust or whomever—who doesn't qualify. That's the policy underlying the qualified disability trust recovery rules. That's why, with the amendments that are consequential to the introduction of a new top marginal rate, it follows. The existing rules reference the previous top marginal rate of 29%, and the new rules would reference or be built upon the new top marginal rates. That policy actually remains consistent.