Can a timer switch for a jetted tub be placed within reach of the tub?
I think you mean Hydromassage Bathtubs… Nothing in the minimum adopted NFPA70 standard would prohibit the switch from being within reach. Of course assuming when you say jetted tub…you are not talking about a hot tub or spa as defined in the National Electrical Code. If you fill it, circulate water in it and you drain it after each use…you have a typical Hydromassage bathtub.
However, if it eases your mind , the circuit providing electricity to that Hydromassage tub , that is supplying that switch and finally controlling that readily accessible Hydromassage bathtub will be GFCI protected.
I guess I should add…Canada sees it slightly different that we do here in America…if in Canada do as the Canadians do…keep it 3’ away…EH
That is a big assumption with homeowner installed tubs. Some are not protected at all. Some are protected before the timer. Some are protected after the timer in which case the timer’s metal cover plate (yes there are plenty of those around) may not be protected. And that is why a home inspector is needed. 
If there is a timer switch for this specific Hydromassage bathtub then I would call that an associated component and require GFCI protection ahead if that switch in order to protect the Hydromassage bathtub and its associated components per 680.71.
But let me tell you…as a home inspector I would not call that out as a high level concern IF protected…just because it is within reach.
Ease being that you have “done” your job and verified that the GFCI is present and accounted for. Even if it was not required at the time the house was build…GFCI’s should always be recommended.