ASKWB

Wife or Husband is one family member in relation to an employee under West Bengal Health Scheme. Medical benefit is extended to the employee as well as to the family members. If a Govt. employee is enrolled under this Scheme the wife/ husband of that employee is one beneficialry; no matter she/ he is working or not. If working to a Govt./ Govt. Aided School M.A. is admissible to her /him.

As per Rule 5 of WBSR, pay means the amount drawn by a Government employee as the pay, other than special pay or pay granted in view of his personal qualifications, which has been sanctioned for a post held by him substantively.
As per existing order (No. 4730-F dated 25/05/99) of TA/DA, pay is defined as per the quoted rule of WBSR.
As per sub-rule (h) of Rule 3 of West Bengal Revision of Pay & Allowances '09, basic pay in the revised pay structure means the pay drawn in the prescribed pay band plus applicable grade pay but does not include any other type of pay.
So, this is really unfortunate as you said.
As per T.R. Form No. 23 (West Bengal Form No. 2446B) there is a provision of taking advance regarding TA/DA. But no provision for arear.
Then why an employee accept DA rate in pre-revised scale?

yes, there is an order. i am going to upload it very soon.

Last date of enrollment in Health Scheme was 31.12.2010. If deputation is after enrollment under heath scheme then the employee is eligible to all sort of benefits of WBHS 2008. There is no separate order related to this till now.