Traditionally group disability insurance is not portable if offered under a standard group long term disability plan (aka LTD).
However, if the policy is purchased as part of a guaranteed issue group plan, the policy may be portable by the insured, this depends on the carrier and their practices regarding such things.
The portability of disability insurance depends on how the policy was set up at point of purchase. If it was an individually underwritten plan and paid for by the owner, then yes it cannot be cancelled due to change of occupation or health. If the plan was through a group it is advised to ask the benefit administrator or human resources director how the policy was set up. The short answer is some group disability policies are portable and some are not.
However, if the policy is purchased as part of a guaranteed issue group plan, the policy may be portable by the insured, this depends on the carrier and their practices regarding such things.
Some group insurance plans do offer the ability to convert your group coverage under certain circumstances (check with your provider).
If you have further question, or feel that I could be of assistance, please do not hesitate to contact me.