Yes, you can have a one common Interrupt Service Routine (ISR) for all interrupt vectors on the device. The common ISR name, _DefaultInterrupt, can be declared as:
If there is no user-defined _DefaultInterrupt, the compiler will define one consisting of a break and a reset, which will cause the debugger to halt. If no debugger is present, it will cause the device to reset.
Consider that you have configured four timer interrupts, but only two ISRs with interrupt vector names for two timer interrupts are defined:
The Interrupt Vector Table (IVT) location for Timer1 and Timer2 will have instruction to jump to ISR _T1Interrupt and _T2Interrupt respectively. ISRs for _T3Interrupt and _T4Interrupt are not defined. So, IVT locations for Timer 3 and 4 will be empty. The compiler assigns the undefined IVT locations with a jump instruction to jump to default ISR defined as _DefaultInterrupt.
So, IVT locations of Timer 3 and 4 will have a jump to ISR _DefaultInterrupt(). When interrupt through either Timer 3 or 4 occurs, the execution will jump to ISR _DefaultInterrupt().