Python ElementTree xml output to csv with conditions

I have the following script:

import xml.etree.ElementTree as ET
import csv

tree = ET.parse('registerreads.xml')
root = tree.getroot()[3]

with open('registerreads.csv', 'wb') as fout:
    writer = csv.writer(fout)
    row = ['Value', 'ReadingTime', 'EntityId']
    writer.writerow(row)
    for channel in tree.iter('Channel'):
        for exportrequest in channel.iter('ExportRequest'):
            entityid = exportrequest.attrib.get('EntityID')
            for meterread in channel.iter('Reading'):
                read = meterread.attrib.get('Value')
                date = meterread.attrib.get('ReadingTime')
                row = [read[:-2], date[:10], entityid]
                print ', '.join(row)
                writer.writerow(row)

which parses and outputs from this part of the tree in the xml file:

<Channel StartDate="2016-02-14T00:00:00-06:00" EndDate="2016-02-15T00:00:00-06:00" TimeZone="CentralUS" IsRegister="true" MarketType="Electric" IntervalLength="-1" NumberOfDials="5" PulseMultiplier="-1" PressureCompensationFactor="1" IsReadingDecoded="true" ReadingsInPulse="false">
      <ChannelID ServicePointChannelID="74325661:150" />
      <Readings>
        <Reading Value="8.4" ReadingTime="2016-02-14T17:05:00-06:00" StatusRef="1" />
      </Readings>
      <ExportRequest RequestID="270" EntityType="ServicePoint" EntityID="74325661" RequestSource="Scheduled" />
    </Channel>
    <Channel StartDate="2016-02-14T00:00:00-06:00" EndDate="2016-02-15T00:00:00-06:00" TimeZone="CentralUS" IsRegister="true" MarketType="Electric" IntervalLength="-1" NumberOfDials="5" PulseMultiplier="-1" PressureCompensationFactor="1" IsReadingDecoded="true" ReadingsInPulse="false">
      <ChannelID ServicePointChannelID="74325661:301" />
      <Readings>
        <Reading Value="173.2" ReadingTime="2016-02-14T00:00:00-06:00" StatusRef="1" />
        <Reading Value="209.1" ReadingTime="2016-02-15T00:00:00-06:00" StatusRef="1" />
      </Readings>
      <ExportRequest RequestID="270" EntityType="ServicePoint" EntityID="74325661" RequestSource="Scheduled" />
    </Channel>

for these results:
Value,ReadingTime,EntityId,ServicePointChannelID
8,2016-02-14,74325661
173,2016-02-14,74325661
209,2016-02-15,74325661

I want the script to grab only the data where <ChannelID ServicePointChannelID="74325661:301" /> is the :301.  The First data row in the output file is actually from a :150, no a :301.

Any help is appreciated.