Rych,
As you said, it depends on how competitive the event is as well as how it's organized. In sanctioned road races with licensed categories it's pretty typical to have feed zones where water bottles and or food in musette bags is handed up to riders. For reliable feeds we typically arrange for team support from friends, spouses, etc. to make sure we get a feed and get what we want in the bottles we receive. In some events, especially if they're long or run in hot weather there are neutral feeds where volunteers hand up water bottles to any riders. No guarantee whether you'll get water, an energy drink you can tolerate or if they run out or the event isn't as well organized you might get nothing.
For 110km in reasonable weather I'd probably go with two large bottles on the bike if I didn't have a team feed. If it's particularly hot or I suspect I'm going to need more fluids I'll definitely carry a third bottle in a jersey pocket if I don't have a prearranged team feed. That's paid off big time in several hot races when they ran out at the neutral feeds and I was carrying enough to get me to the finish. Everyone hates carrying extra weight, especially if the course is hilly and the neutral feeds are great and you don't need the extra bottle or the extra large bottles but if the weather is hot, the race is long or you have doubts about getting a hand up it's worth it.
But for less competitive events like GranFondos, century rides and day tours then it's common to stop at some or all of the supported rest stops for a quick refuel before getting on your way. It's even typical for fast moving groups to talk it over and collectively stop if the group is working well together and folks would prefer to keep it together.
As it sounds like it's your first event of this length I'd probably err on the conservative side and take at least two full size bottles as well as some gel blocks, energy bars, gu or banannas in your pockets so that you're reasonably well set but still plan on taking a quick stop at the 55km feed if you need it. BTW, you should only plan on consuming somewhere around 250-300 calories per hour including any energy drink in your bottles. So depending on the course and your expected pace that's something like four energy bars or packages of shot blocks along with some energy drink so it's not exactly stuffed pockets. Most folks can't digest more than about 280-300 calories per hour while riding so you don't need to carry an entire grocery store.
Good luck and have a great ride,
-Dave
