Twisted Bredon-Illman Cohomology is a Morita Invariant

We show that the twisted Bredon-Illman cohomology defined by Mukherjee-Mukherjee applied to compact Lie group action groupoids is Morita-invariant. This cohomology uses coefficient systems twisted over the discrete tom Dieck equivariant fundamental groupoid. To show Morita invariance, we use bibundles to transfer coefficient systems from one groupoid to another Morita equivalent one. This generalises results of Pronk-Scull on ordinary Bredon-Illman cohomology by removing both the finite isotropy condition and restrictions on the coefficient systems.