As there is no requirement to do any additional Dual Instrument Instruction for a Night Qualification, the IMC rating no longer has any relevance with regard to credits.
Instructors should bear in mind that the only dual instrument training under the new system will have been Ex 19 lasting probably no more than an hour, so some additional instrument training may be necessary in practice.
JAR -FCL night requirements are in JAR-FCL 1.125(c). There have been no changes to this requirement since it was printed over 4 years ago.