Beneficiaries do use carryover basis for securities distributed in-kind if no election is made to recognize gain at the trust or estate level. It sounds like there would be no benefit to making that election in the case Margaret describes because the trust has had gains thus far.
The election allows recognition of gain at the trust/estate level at the time of distribution, and it must be applied to all in-kind distributions during the tax year and not be applied on an asset-by-asset basis. If this election is made, then the beneficiary would then use a stepped up basis when the security is ultimately disposed of. This strategy may be beneficial when the trust has unused capital losses that could absorb the gain, but Margaret's client doesn't have this scenario, so this would likely not be advantageous. It's also has no benefit if the beneficiary will incur more tax than the trust, if the beneficiary will hold the security for a long time and thereby deferring gain for that extended period, or if planning to hold it until death at which time it would receive the stepped up basis.