I can only assume that the rationale behind Ballynoe is to provide better access to the area around Rushbrooke Links. Overall it would serve close to 400 houses there and maybe another 30-40 one-off houses in the area. However, the southern end of Rushbrooke Links is as close to Rushbrooke station and could be facilitated by a direct footpath. Unless thereís further zoning in the area, the station seems marginal compared to others around Cork. Itís also worth noting that Rushbrooke Links also has a direct bus service to Cork.
One thing that may be a factor is that the road bridge at Belvelly is struggling for capacity and that upgrade to the rail service in Great Island May be seen as a cheaper option than building a completely new road bridge off the island and link road up to Carrigtwohill. Back of the envelope calculation for that would be in the Ä80m-Ä120m range considering the terrain (or more accurately water) so the cost of a new station and increased rail frequency pales in comparison.
The main point to note with Tivoli is that what goes there is now firmly decided (and nothing will happen til 2028 when the Port of Cork vacate the site). However, the two proposals are either high density housing for up to 10k people or merging the Mercy Hospital and South Infirmary to create a new hospital on the site that would be one of the largest in the country, so either would create demand for a new station and that before considering the existing housing round Lotabeg and employment at the industrial estate. Hopefully thatís just a wait and see as with Port of Cork in there for the foreseeable future there is plenty of time to get a station in place before it becomes useful.