I have a partial answer and I am exploring the problem with a computer now.  In the positive direction, Fournier’s theorem provides a partial answer.  

Fournier’s theorem is a strengthening of Vizing’s theorem and it goes as follows:  Let $D$ be the max degree of your graph $G$.  If the vertices of $G$ that have degree $D$ are independent, then $G$ is class 1.  Let us say that a graph which satisfies this condition is a Fournier graph.

So consider a cycle plus triangles graph $G$ and vertex-3-color $G$ with colors $r, g, b$.  Delete the triangle edges between vertices colored $r, b$.  Then, the resulting graph is Fournier with max degree 4, so it can be edge-4-colored.  So the question remains whether it is possible to reinsert the deleted edges so that $G$ remains class 1.  It turns out, not always (not if there are an odd number of triangles, see the updated question).

All examples with even number of triangles that I have explored are class 1.  Recall that we are considering only simple graphs.

Here is a pretty picture of a C + T graph with 10 triangles.  I edited the answer to include the correct picture.  The previous one had an edge with a 5th color by mistake (my mistake, not the computer).

[![CYCLE PLUS TRIANGLES GRAPH WITH 10 TRIANGLES][1]][1]


Here is a graph with 11 triangles and its Hamiltonian decomposition:

[![C + T graph with 11 triangles and its Hamiltonian decomposition][2]][2]


  [1]: https://i.sstatic.net/l5W5S.png
  [2]: https://i.sstatic.net/wkS4I.png