Shear Bolts??
in my mind, one can define just about any bolt as a shear bolt, so I really have no idea what the original poster is talking about.
All the bolts holding the engine and the pylon are designed to withstand all anticipated rigours of engine failures and in-flight gust loads. It is true however that some gust loads and accompanied aerodynamic loads on the wing can break aircraft wings or other critical structures.
The idea is to make sure that any such aerodynamic loads imposed on the lesser critical pylon (not actually needed for flight) will not break the wing (which is always needed for safe landing). Thus some bolts are designed to be weaker than others.
With that said all such loads are designed to be used in a redundant system which provides many parrell paths to carry these loads so that if any path is broken there will still be plenty of margin for normal flight loads.
The history has many examples of broken or missing bolts in the engine mount pylon system and then sustaining some pretty massive engine failures loads without any cause for alarm..
Of course their is always a limit to our immagination of just how many missing bolts does anybody expect to dispatch with.