Joe,
it seems fairly clear that the only Grand Ducal Hessian units wearing the Prussian pattern shako with the Hessian lion plate in peacetime were the Train Company/Battalion.
Additionally, the personnel of Landwehr Regiments (before the 1888 reorganisation) and later, the exercising Landwehr personnel from the Grand Ducal Hessian Landwehr Districts wore the shako with the Landwehr Cross with inscription "Gott, Ehre, Vaterland". Similarly the permanent staff of the Landwehr Districts wore the shako until replaced by the Pickehaube.
The 1905 supplement to the dress regulations which covered the Grand Ducal Mecklenburg and Grand Ducal Hessian contingents confirms that the Hessian Landwehr still wore the shako with the Landwehr Cross and inscription "Gott, Ehre, Vaterland"
That being the case, it seems likely that those individuals wearing a plated shako are using former Train-Bataillon shakos.
The dress regulations of 1905 already provided that on mobilzation, the newly formed I./Landwehr-Infanterie-Regiment Nr. 116 would wear the Litewka of Infanterie- (Leibgarde-) Regiment Nr. 115 with the red number 116 on white shoulder straps. Similarly on formation, I./Reserve-Infanterie-Regiment Nr. 116, would wear the Waffenrock of Infanterie- (Leibgarde-) Regiment Nr. 115 with the red number 116 on white shoulder straps. In both instances above, the NCOs wore white linen litzen as opposed to the silver of the ILR 115 NCOs.
Regards
Glenn