Tune in and listen, yes.
Tune in and transmit, no.*
* some/most/all amateur radios can be modified to transmit out of the intended range (it is good engineering practice? depends on the radio)
For example, the Yaesu VX-8DR, which is sold at
AES Home page
This radio can receive 400 to 470 MHz, but only transmits 430 to 450 MHz (UHF amateur band).
On the other hand, Motorola UHF radios come in a 400-470 MHz split, and can transmit throughout.
The dilemma is FCC type acceptance......will one radio do amateur, GMRS, MURS, and public safety? Technically, yes. Would that one radio be "type accepted" for each category? Likely not.
Your question is a common one. GMRS radios can be bought through various dealers.
GMRS Outlet LLC