A routed port is specifically not a switch port. You are putting the
no switchport command on the port to disable the switching functions. It becomes a router interface.
SPAN will not work on a switch port which is routed. Some Cisco devices (very few) can use ERSPAN to route SPAN traffic, but the 3560G is not one of them. SPAN and RSPAN are layer-2 only and ERSPAN is across layer-3.
Understanding SPAN,RSPAN,and ERSPAN
Local SPAN: Mirrors traffic from one or more interface on the switch
to one or more interfaces on the same switch.
Remote SPAN (RSPAN): An extension of SPAN called remote SPAN or RSPAN.
RSPAN allows you to monitor traffic from source ports distributed over
multiple switches, which means that you can centralize your network
capture devices. RSPAN works by mirroring the traffic from the source
ports of an RSPAN session onto a VLAN that is dedicated for the RSPAN
session. This VLAN is then trunked to other switches, allowing the
RSPAN session traffic to be transported across multiple switches. On
the switch that contains the destination port for the session, traffic
from the RSPAN session VLAN is simply mirrored out the destination
Encapsulated remote SPAN (ERSPAN): encapsulated Remote SPAN (ERSPAN),
as the name says, brings generic routing encapsulation (GRE) for all
captured traffic and allows it to be extended across Layer 3 domains.
ERSPAN is a Cisco proprietary feature and is available only to
Catalyst 6500, 7600, Nexus, and ASR 1000 platforms to date. The ASR
1000 supports ERSPAN source (monitoring) only on Fast Ethernet,
Gigabit Ethernet, and port-channel interfaces.
The latest information I have is that Cisco is planning to add ERSPAN support to some Catalyst 3K and 4K switches in code versions to be released later in 2016, albeit there were no guarantees.